Combustion kinetics of coal chars in oxygen-enriched environments
Combustion kinetics of coal chars in oxygen-enriched environments
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DOI：
10.1016/j.combustflame.2005.08.039
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发表时间：
2006-03-01
影响因子：
4.4
通讯作者：
Shaddix, CR
中科院分区：
文献类型：
--
作者：
Murphy, JJ;Shaddix, CR
目前正在积极研究增氧和燃氧煤粉燃烧，以实现减排和降低烟道气净化成本，以及在煤层气和提高采油方面的应用。为了充分理解中试试验的结果，并通过CFD模型准确地预测放大性能，需要准确的速率表达式来描述这些非常规燃烧条件下的煤焦燃烧。在本文中，我们测量了两种煤粉煤焦在常规气氛和富氧气氛中的燃烧速率。燃烧驱动的气流床反应器配备了光学颗粒测温诊断装置和快速熄灭取样探头。对高谷次烟煤和美国东部的一种高挥发分烟煤进行了研究，氧浓度范围为6~36摩尔%，气体温度为1320~1800K。这些实验结果表明，尽管煤焦颗粒在高氧环境中的燃烧速率较高，但它们在高氧环境下燃烧的动力学控制增强。使用单膜氧化模型在整个氧浓度范围内成功地对数据进行了经验拟合。简单的n阶阿累尼乌斯方程和n阶朗缪尔-辛舍伍德动力学方程都很好地拟合了数据。与整个数据集的拟合相比，n阶阿累尼乌斯表达式与富氧和耗氧数据的局部拟合产生较低的残差。这些拟合表明，表观反应级数在接近扩散极限的贫氧条件下为0.1，在富氧条件下为0.5。对工作倦怠的预测与测量结果吻合良好。对于在氧气耗尽的环境中燃烧，预测的焦炭颗粒温度往往较低。(C)2005年，燃烧研究所。爱思唯尔公司出版，版权所有。
Oxygen-enhanced and oxygen-fired pulverized coal combustion is actively being investigated to achieve emission reductions and reductions in flue gas cleanup costs, as well as for coal-bed methane and enhanced oil recovery applications. To fully understand the results of pilot scale tests and to accurately predict scale-up performance through CFD modeling, accurate rate expressions are needed to describe coal char combustion under these unconventional combustion conditions. In the work reported here, the combustion rates of two pulverized coal chars have been measured in both conventional and oxygen-enriched atmospheres. A combustion-driven entrained flow reactor equipped with an optical particle-sizing pyrometry diagnostic and a rapid-quench sampling probe has been used for this investigation. Highvale subbituminous coal and a high-volatile eastern United States bituminous coal have been investigated, over oxygen concentrations ranging from 6 to 36 mol% and gas temperatures of 1320-1800 K. The results from these experiments demonstrate that pulverized coal char particles burn under increasing kinetic control in elevated oxygen environments, despite their higher burning rates in these environments. Empirical fits to the data have been successfully performed over the entire range of oxygen concentrations using a single-film oxidation model. Both a simple nth-order Arrhenius expression and an nth-order Langmuir-Hinshelwood kinetic equation provide good fits to the data. Local fits of the nth-order Arrhenius expression to the oxygen-enriched and oxygen-depleted data produce lower residuals in comparison to fits of the entire dataset. These fits demonstrate that the apparent reaction order varies from 0.1 under near-diffusion-limit oxygen-depleted conditions to 0.5 under oxygen-enriched conditions. Burnout predictions show good agreement with measurements. Predicted char particle temperatures tend to be low for combustion in oxygen-depleted environments. (c) 2005 The Combustion Institute. Published by Elsevier Inc. All rights reserved.