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Is the Wheeler-Jonas Equation Applicable to Describe the Breakthrough Curve of an Oxidizing Gas: Ozone Wheeler-Jonas方程是否适用于描述氧化气体臭氧的穿透曲线
臭氧是ASHRAE标准145.2-2011中测试氧化性气体的标准污染物。在非工业建筑中,臭氧通常通过活性炭(AC)去除。在实践中,过滤器的更换频率是一个关键问题。惠勒-乔纳斯方程(WJE)被广泛用于描述AC去除有机蒸汽的穿透曲线。一些研究报告,WJE也适用于一些无机气体,包括酸性气体-氯和碱性气体-氨。本文首先研究了氧化性气体WJE的适用性- 臭氧这些实验是在精心设计的小型试验台上进行的。结果表明,WJE不适用于臭氧。关于WJE,有两个假设:恒定的吸附动力学和忽略轴向扩散。文献综述证实了多种臭氧AC反应机理与不同的反应活性相结合,这表明假设的恒定吸附动力学不适用于臭氧AC反应。最后,提出了一个由偏微分方程(PDE)描述的新的质量平衡模型,该模型引入了轴向扩散项和伴随指数失活的一级动力学。 PDE解与实验数据吻合良好。Péclet数由PDE模型估算的轴向扩散系数计算得出。较大的值表明轴向扩散不显著。因此,WJE中假设的恒定吸附动力学被认为是其不适用于臭氧的主要原因。引用:2016年冬季会议,佛罗里达州奥兰多,会议论文
Ozone is the criteria pollutant with respect to oxidizing gases to be tested in ASHRAE Standard 145.2-2011. In non-industrial buildings, ozone is normally removed by activated carbon (AC). In practice, how often the filters should be replaced is a key question. The Wheeler-Jonas equation (WJE) is widely used for describing breakthrough curves of organic vapours removal by AC. Some studies reported the WJE is also applicable of some inorganic gases including the acid gas - chlorine and the basic gas - ammonia.This paper firstly investigated applicability of the WJE of an oxidizing gas - ozone. The experiments were conducted on a well-designed bench-scale test rig. The results indicated that the WJE does not work for ozone.There are two assumptions associating with the WJE, constant adsorption kinetics and neglecting axial diffusion. Multiple ozone-AC reaction mechanisms combined with different reactivities were confirmed from the literature review, which indicate the assumed constant adsorption kinetics is improper for ozone-AC reacitons.Finally, a new mass balance model described by a partial differential equation (PDE) which introduces the axial diffusion term and first order kinetics accompanied by exponential deactivation was proposed. The PDE solution is in good agreement with the experimental data. The Péclet number was calculated with the estimated axial diffusion coefficient from the PDE model. The large value indicates the axial diffusion is not significant. Therefore, the constant adsorption kinetics assumed in the WJE is considered to be the major reason of its inapplicability of ozone.
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