Ultrasound assisted Peroxone, a novel air pollution control technique

空气污染是许多工业过程中持续关注的问题。挥发性有机化合物(VOCs)是一类重要的空气污染物，因为它们参与烟雾形成(对流层臭氧)，以及一些VOCs的有毒和/或致癌性质。虽然已经有有效的战略来处理大量和集中的VOC排放，但小的和稀释的排放往往得不到处理，尽管它们的总排放量很大。一个例子是天然气部门乙二醇脱水装置的苯排放，加拿大每年排放约2000吨，分布在数千个小来源。*过去受到关注的废气处理技术是过氧化氢技术，它是过氧化氢和臭氧的组合，用于对污染物进行化学氧化。限制这项技术有效性的是臭氧的低溶解度，因为导致污染物降解的反应发生在水相中。此外，臭氧在过氧化物酮体系中具有高度的反应性，反应时间不到一毫秒。因此，只有靠近液体表面的一层非常薄的层具有化学活性。然而，臭氧和过氧化氢被认为是云中有效的污染物氧化剂，这要归功于云滴的精细分散。因此，以雾的形式使用Peroxone过程可以大大提高效率。*平均液滴尺寸在20微米或更小的水雾可以用超声波产生，类似于云中的液滴大小。因此，如果过氧化氢溶液以超声波喷雾的形式提供，预计过氧化氢系统将大大提高效率。拟议项目的目的是通过实验和模拟测试这一假设，并将其作为开发一类新的有效的高级氧化技术的基础，用于废气处理。*这项项目符合整体研究计划，长期目标是开发一套能够处理石油和天然气行业和制造业排放的空气污染物的废气处理技术。我的团队目前正在研究的其他技术包括生物过滤和紫外线降解。*这个项目所需的所有设备都在我的实验室里，除了超声波喷雾发生器。实验将以苯为污染物，在广泛的实验条件下进行。苯的降解将通过进水和出水样品的气相色谱分析来测量。*在建模方面，将开发一个全面的化学机理，以帮助解释实验数据，并帮助优化工艺，以扩大规模的目标。我的研究小组在气相中模拟这些反应方面有丰富的经验。由于离子的存在，以及不同的反应速率常数和浓度，液相体系是不同的。我们将对所有相关反应的动力学进行全面的文献搜索，并将反应包括在模型中。*通过传质模型，我们将验证传质平衡时间足够短的假设，以证明完全混合的假设是合理的。还将对雾滴的蒸发和合并进行额外的计算，以确定雾滴的最终命运。这一考虑将对最终将该工艺扩大到工业规模具有重要意义。*如果研究成功，将寻求工业伙伴的参与，以开发和建立该工艺的试验规模版本，并在实际工业现场进行测试。

Air pollution is an ongoing concern for many industrial processes. Volatile organic compounds (VOCs) form an important class of air pollutants because of their involvement in smog formation (trophospheric ozone), and the toxic and/or carcinogenic nature of some VOCs. While effective strategies exist to treat large and concentrated VOC emissions, small and dilute emissions are often untreated although their aggregate emission is substantial. An example is benzene emissions from glycol dehydration units in the natural gas sector, with an annual emission of about 2000 tons in Canada, spread over several thousands of small sources.*A waste gas treatment technique that received interest in the past is the peroxone technique, which is the combination of hydrogen peroxide and ozone for the chemical oxidation of pollutants. What limits the effectiveness of this technique is the low solubility of ozone, because the reactions leading to pollutant degradation occur in the water phase. In addition, ozone is highly reactive in peroxone systems, with reaction times of less than a millisecond. As a result, only a very thin layer near the liquid surface is chemically active. However, ozone and hydrogen peroxide are known to be effective pollutant oxidizers in clouds, thanks to the finely dispersed nature of cloud droplets. It follows that the peroxone process can be made substantially more effective by using it in the form of a mist.*Mists with a mean droplet size of 20 micrometer or less can be created with ultrasonic waves, similar to the droplet size in clouds. Hence, it is expected that a peroxone system will be substantially more effective if the hydrogen peroxide solution is delivered as an ultrasonic spray. The objective of the proposed project is to test this hypothesis experimentally and through modeling, and to use it as a basis for developing a new class of efficient advanced oxidation techniques for waste gas treatment.*This project fits into an overall research programme with the long-term objective of developing a suite of waste gas treatment techniques capable of treating air pollutants emitted by the oil and gas sector and the manufacturing sector. Other techniques that are currently being studied by my group are biofiltration and ultraviolet degradation. *All the required equipment for this project is available in my lab, with the exception of an ultrasonic spray generator. Experiments will be carried out with benzene as the pollutant, in a wide range of experimental conditions. Benzene degradation will be measured by gas chromatography analysis of influent and effluent samples. *On the modeling side, a comprehensive chemical mechanism will be developed to help interpret the experimental data, and to aid the optimization of the process with the objective of scaling up. My research group has extensive experience with modeling these reactions in the gas phase. The liquid phase system is different due to the presence of ions, and to the different reaction rate constants and concentrations. We will carry out a comprehensive literature search on the kinetics of all the relevant reactions, and include the reactions in the model.*By means of mass transfer modeling we will verify the assumption that the mass transfer equilibration time is sufficiently short to justify the assumption of complete mixing. Additional calculations on droplet evaporation and coalescence will be carried out to determine the eventual fate of the mist droplets. This consideration would be of importance in the eventual scale-up of the process to industrial scale.*If the research is successful, participation of industrial partners will be sought to develop and build a pilot scale version of the process, and test it at an actual industrial site.