Modeling of the SCR reactor for coal-fired power plants: Impact of NH3 inhibition on Hg0 oxidation
Modeling of the SCR reactor for coal-fired power plants: Impact of NH3 inhibition on Hg0 oxidation
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DOI：
10.1016/j.cej.2014.06.114
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发表时间：
2014-12
影响因子：
15.1
通讯作者：
A. Beretta;N. Usberti;L. Lietti;P. Forzatti;M. D. Blasi;A. Morandi;C. L. Marca
中科院分区：
文献类型：
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作者：
A. Beretta;N. Usberti;L. Lietti;P. Forzatti;M. D. Blasi;A. Morandi;C. L. Marca
建立了蜂窝状催化剂SCR反应器的一维+一维非均相模型，采用集总法描述气固传质，微分法描述催化剂壁内的扩散和反应，求解了反应组分沿着轴向和径向的质量平衡。该模型描述了共存的脱NOx反应和高度期望的氧化Hg0。这是众所周知的，从文献中，Hg0的转化是负面影响的NH3，但这种抑制的程度是不确定的，因为固有的复杂性的汞形态测量。因此，我们应用该模型来检查的浓度和反应速率的整体墙内的轮廓和理解的方式和程度的干扰Hg0氧化的NH3。本征动力学参数的估计是从商业V基催化剂的实验室规模和中试规模测试中获得的，这使得分析集中在现实条件下。的脱硝和汞的氧化过程都受到外部和内部的传质限制，但从扩散的动力学控制的情况下，脱硝反应更强。因此，NH3浓度在沿着径向坐标和沿着轴向坐标上的衰减比Hg0浓度的衰减更明显。在实践中，决定NH3抑制的整体影响的主要操作参数是面积速度，即全规模反应器的尺寸。尽管如此，参数分析提供了有用的元素，设想所需的催化剂特性，可以促进Hg0转化和最小化NH3抑制。
A 1D + 1D heterogeneous model of the SCR reactor with honeycomb monolith catalyst is developed; it solves the mass balances of the reacting species along the axial and radial direction, using a lumped approach to describe the gas–solid mass transfer and a differential approach to describe diffusion and reaction within the catalyst wall. The model describes the coexistence of the DeNOXreaction and the highly desired oxidation of Hg0. It is well known from the literature that the conversion of Hg0is negatively affected by NH3, but the extent of such an inhibition is uncertain because of the inherent complexity of the mercury speciation measurement. We thus apply the model to examine the concentration and reaction rate profiles inside the monolith wall and comprehend the way and extent of the interference of NH3on Hg0oxidation. The estimate of the intrinsic kinetic parameters was obtained from lab scale and pilot scale tests over commercial V-based catalysts, which allowed to focus the analysis on realistic conditions. The DeNOXand the Hg oxidation processes are both affected by external and internal mass transfer limitations, but the kinetic control from diffusion is stronger in the case of the DeNOXreaction. Thus along the radial coordinate and along the axial coordinate, the decay of NH3concentration is more pronounced than the decay of Hg0concentration. In practice, the main operating parameter which determines the integral impact of NH3inhibition is the area velocity, that is the sizing of the full scale reactor. Still, a parametric analysis provides useful elements for envisaging the desired catalyst characteristics which can promote Hg0conversion and minimize NH3inhibition.