Abstract Alkali metals, especially Na, are generally accepted as the primary cause of serious ash-related problems in the industrial applications of pulverized coal. This paper investigates the effects of different variables, including particle size, ambient temperature, O2 mass fraction, and atmospheres: O2/N2 and O2/CO2 at particle level. The fictitious domain method (FDM) provides a true direct numerical simulation (TDNS) for the investigation. Computational results show the correlation between alkali metals release and carbon consumption during char particle combustion. Here, high ambient temperature is more positive to alkali metals release than carbon consumption. In an oxygen-dominated atmosphere, a small amount of CO2 tends to form a higher temperature field than N2, which promotes a greater release of alkali metals. This paper also investigates the specific effects of volume fraction and non-uniform distribution of particles for the combustion of particle groups. The computational results show that both temperature field and alkali metals release are significantly affected by the volume fraction of particles. The effects of the non-uniform distribution of particles, e.g., uniform distribution, dense distribution on the windward side, dense distribution on the leeward side, and asymmetric distribution, on temperature field and alkali metals release vary with different volume fractions of particles. As such, the non-uniform distribution of particles plays a role in changing the mass transfer of the oxidant and the heat transfer.

中文翻译：

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炭颗粒群燃烧过程中碱金属释放影响的数值研究

摘要 碱金属，尤其是钠，被普遍认为是煤粉工业应用中严重灰分问题的主要原因。本文研究了不同变量的影响，包括颗粒大小、环境温度、O2 质量分数和大气：颗粒级别的 O2/N2 和 O2/CO2。虚拟域方法 (FDM) 为调查提供了真正的直接数值模拟 (TDNS)。计算结果显示了炭颗粒燃烧过程中碱金属释放与碳消耗之间的相关性。在这里，高环境温度对碱金属释放比碳消耗更有利。在以氧为主的大气中，少量的 CO2 往往会形成比 N2 更高的温度场，从而促进碱金属的更大释放。本文还研究了体积分数和粒子的非均匀分布对粒子群燃烧的具体影响。计算结果表明，温度场和碱金属释放均受颗粒体积分数的显着影响。颗粒分布不均匀，如均匀分布、迎风侧密分布、背风侧密分布、不对称分布等，对温度场和碱金属释放的影响随颗粒体积分数的不同而不同。因此，颗粒的不均匀分布在改变氧化剂的传质和传热方面起作用。计算结果表明，温度场和碱金属释放都受到颗粒体积分数的显着影响。颗粒分布不均匀，如均匀分布、迎风侧密分布、背风侧密分布、不对称分布等，对温度场和碱金属释放的影响随颗粒体积分数的不同而不同。因此，颗粒的不均匀分布在改变氧化剂的传质和传热方面起作用。计算结果表明，温度场和碱金属释放都受到颗粒体积分数的显着影响。颗粒分布不均匀，如均匀分布、迎风侧密分布、背风侧密分布、不对称分布等，对温度场和碱金属释放的影响随颗粒体积分数的不同而不同。因此，颗粒的不均匀分布在改变氧化剂的传质和传热方面起作用。背风侧密集分布，不对称分布，温度场和碱金属释放随颗粒体积分数不同而变化。因此，颗粒的不均匀分布在改变氧化剂的传质和传热方面起作用。背风侧密集分布，不对称分布，温度场和碱金属释放随颗粒体积分数不同而变化。因此，颗粒的不均匀分布在改变氧化剂的传质和传热方面起作用。