Using ultraviolet (UV) radiation or ozone (or both) to oxidize air pollutants, such as volatile organic compounds (VOCs) is a well-established treatment method in the chemical process industries (CPI). What is not so well known, however, is that for most pollutants, the oxidation products of UV/O3 treatment, such as O3, formaldehyde and a whole range of other semi-oxidized compounds, can be significantly more hazardous than the original VOC, says Nicolai Bork, product manager – Industrial Pollution Control at Infuser ApS (Copenhagen, Denmark; www.infuser.eu). “Alarmingly, we see many installations using just UV/O3 where factory owners have never been informed about these issues.”
Infuser has taken conventional UV/O3 technologies a step further by incorporating a catalytic filter to the normal UV-treatment section. Developed in close collaboration with the University of Copenhagen, the company’s Climatic air-purification technology (diagram) is based on accelerating the self-cleansing mechanisms of the atmosphere — namely, a carefully adjusted combination of gaseous oxidants, water vapor and UV light, explains Bork. This produces OH radicals that oxidize VOCs into oxidation products (OxVOCs) that precipitate out of the gas phase as aerosol particles. A second-stage treatment, using a multibed O3 -removal catalyst with VOC-adsorption capabilities, performs O3 removal and oxidation of the semi-oxidized VOCs to CO2. Furthermore, the filter is designed to capture the produced aerosol particles. For industrial applications, an automated washing of the filter medium can be installed for large-scale continuous operation, he says.
Conventional cleaning technologies, such as adsorption on activated carbon have pressure drops that are 10–15 times higher that a Climatic system, which can translate to 20–100 kW of saved energy for fan power alone, says Bork.
The process has been demonstrated at a leading wind-turbine OEM factory in Europe, which started up in 2017. Four units, totaling 210,000 m3/h, have been continuously reducing styrene emissions by more than 90%, while saving the operator “significant costs” of replacing activated carbon. The company is also targeting other applications in the styrene and polymer industries, says Bork.
