Fundamentals of energy efficient precipitation and inactivation of COVID-19 aerosols by means of an ozone-free electrostatic precipitator designed for indoor use.

气溶胶被视为传播新冠肺炎和其他病毒或细菌感染的决定性途径。主要的液体气溶胶在空气中干燥非常快，形成尺寸从0.1到100微米的残留气溶胶。由于沉积速率很低，大约10微米以下的气溶胶可以在室内空气中积累并达到临界浓度。同时，小于5微米的大小范围被怀疑是传播感染的最重要因素。静电除尘器(ESP)非常适合于分离0.1至100微米的细小气溶胶。ESP的极低压降(仅几帕)允许与低噪音通风机结合使用。低噪音是室内应用气溶胶除尘器能否被接受的一个重要因素。此外，静电除尘器提供了通过紫外线或气体离子使沉淀气溶胶失活的便捷途径。然而，一个问题是电晕放电中臭氧的形成，到目前为止，电晕放电被用作所有电除尘器气溶胶充电的气体离子来源。臭氧的浓度超过约70微克/立方米，被认为是剧毒的。本项目旨在为建造一种适合室内使用的新型无臭氧电除尘器提供基础知识。由于臭氧在较高温度下是不稳定的，电晕线的适度加热应该足以抑制臭氧的形成。应讨论的其他方面包括紫外线对病毒模型气溶胶的灭活作用、臭氧与紫外线之间的相互作用以及在活动电晕区内挥发性有机化合物的反应可能形成的二次气溶胶。

Aerosols are seen as a decisive pathway for spreading COVID-19 and other viral or bacterial infections. The primary liquid aerosols are drying very fast in the air, forming residual aerosols in the size range from 0.1 to 100 µm. Due to the low deposition rate, aerosols below about 10 µm can accumulate in indoor air and reach critical concentrations. Meanwhile, the size range below 5 µm is suspected to be the most important for spreading infections. Electrostatic precipitators (ESPs) are ideally suited for the separation of fine aerosols in the size range from 0.1 to 100 µm. The extremely low pressure drop of ESPs (amounting to a few Pa only) allows the combination with low-noise ventilators. Low noise is an important factor for the acceptance of aerosol precipitators for indoor applications. More¬over, ESPs offer easy access for the inactivation of the precipitated aerosol by means of UV light or gas ions. A problem, however, is the formation of ozone in the corona discharges which are used, so far, as a source of gas ions for aerosol charging in all ESPs. Ozone is regarded as highly toxic in concentrations exceeding about 70 µg/m³. The present project intends to provide the basic knowledge for building a new type of ozone-free ESPs, which is well-suited for indoor use. As ozone is instable at higher temperatures, a moderate heating of the corona wire should be sufficient to suppress ozone formation. Further aspects which shall be addressed are the inactivation of virus model aerosols by UV light, interactions between ozone und UV, and the possible formation of secondary aerosols by reactions of VOCs in the active corona zone.