Characterization of ashes from a 100kWth pilot-scale circulating fluidized bed with oxy-fuel combustion
Characterization of ashes from a 100kWth pilot-scale circulating fluidized bed with oxy-fuel combustion
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DOI：
10.1016/j.apenergy.2011.03.007
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发表时间：
2011-09
期刊：
影响因子：
11.2
通讯作者：
Yinghai Wu;Chunbo Wang;Yewen Tan;L. Jia;E. Anthony
中科院分区：
文献类型：
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作者：
Yinghai Wu;Chunbo Wang;Yewen Tan;L. Jia;E. Anthony
在一台100千瓦的小型循环流化床(CFBC)氧燃烧装置上进行了富氧燃烧试验。以煤和石油焦为燃料，加入不同的石灰岩(固定的Ca：S摩尔比)与燃料预混，进行SO2捕集。采集了该装置生产的床灰(BA)和飞灰(FA)样品，并对其进行了表征，以获得灰样的物理和化学性质。所用的表征方法包括X射线荧光(XRF)、X射线衍射(XRD)、炭碳和游离石灰分析、热重分析(TGA)和表面分析。这项工作的主要目的是对富氧燃烧产生的循环流化床锅炉灰烬进行表征，以更好地了解燃烧过程，并找出与传统空气循环燃烧锅炉产生的灰烬有何显著差异。在典型的沸腾炉温度(∼850°C)下，空气和氧燃料沸腾炉之间的硫捕获机制的主要区别在于，在空气燃烧的情况下，石灰石脱硫剂被焙烧，而二氧化碳的分压足够高，以防止焙烧，因此硫化过程应该模仿加压沸腾炉(PFBC)中看到的过程。在这里，飞灰中的焦碳含量远远高于床灰中的焦碳含量，与传统的商用空气循环流化床机组的灰分相比也是很高的。此外，对床层和飞灰中游离石灰含量的测量表明，未反应的钙脱附剂主要以CaCO3的形式存在，这表明富氧燃烧器中的硫是通过直接硫化作用进行的。该装置氧燃料的石灰石利用率普遍低于工业规模的空气燃烧CFBC，在相对较高的温度下运行的石油焦燃烧时，石灰石的性能更好。飞灰的Brunauer-Emmett-Teller(BET)比表面积和孔体积远大于床灰，且飞灰样品中以较小尺寸的孔为主。
Oxy-fuel combustion experiments have been carried out on an oxygen-fired 100 kWthmini-circulating fluidized bed combustion (CFBC) facility. Coal and petroleum coke were used as fuel together with different limestones (and fixed Ca:S molar ratios) premixed with the fuel, forin situSO2capture. The bed ash (BA) and fly ash (FA) samples produced from this unit were collected and characterized to obtain physical and chemical properties of the ash samples. The characterization methods used included X-ray fluorescence (XRF), X-ray diffraction (XRD), char carbon and free lime analysis, thermogravimetric analysis (TGA), and surface analysis. The main purpose of this work is to characterize the CFBC ashes from oxy-fuel firing to obtain a better understanding of the combustion process, and to identify any significant differences from the ash generated by a conventional air-fired CFBC. The primary difference in the sulfur capture mechanism between atmospheric air-fired and oxy-fuel FBC, at typical FBC temperatures (∼850 °C), is that, in the air-fired case the limestone sorbents calcine, whereas the partial pressure of CO2in oxy-fuel FBC is high enough to prevent calcination, and hence the sulfation process should mimic that seen in pressurized FBC (PFBC). Here, the char carbon content in the fly ash was much higher than that in the bed ash, and was also high by comparison with ash obtained from conventional commercial air-firing CFBC units. In addition, measurements of the free lime content in the bed and fly ash showed that the unreacted Ca sorbent was present primarily as CaCO3, indicating that sulfur capture in the oxy-fuel combustor occurredviadirect sulfation. Limestone utilization for oxy-fuel combustion in this unit was generally lower than that in industrial-scale air-firing CFBCs, with better limestone performance found during combustion of petcoke running at relatively higher temperatures. The Brunauer–Emmett–Teller (BET) surface area and also the pore volume in the fly ash were much higher than in the bed ash and smaller size pores predominated in the fly ash samples.