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BREEZE brings eco-friendly air purifiers on board

18 June 2021

Aircraft cabins have an extremely high density of occupation and a limited available air volume. Typically, half of the air is exhausted and the other half is mixed with outside air (normally supplied through the engine – bleed air) and re-circulated into the passenger cabin, with a complete cabin air exchange every 2–3 min. 

In most aircraft, recirculated air passes through High Efficiency Particulate Air (HEPA) filters to extract contaminants suspended in the air (particles, bio-contaminants). These systems are able to capture pollutants such as volatile organic compounds (VOCs) in addition to the particulate filtration.

Other alternative technologies that could be used include electrostatic passive filters/precipitators based on the use of electric fields to remove pollutants, or UVC lamps for air disinfection, but both are susceptible to ozone generation. 

BREEZE developed an innovative air purification filter that can successfully decrease the level of VOC by 85%, ozone by 80% and presented biocontaminant removal properties. The demonstration was done on a lab-scale prototype under laboratory environmental conditions (simulated aircraft ventilation system conditions).

The technology combines adsorption with photocatalysis (PCO). The PCO process consists of the generation of highly reactive species, such as hydroxyl radicals (•OH), which are capable of mineralising organic matter and destroying ozone and bio-contaminants. This occurs when a photocatalyst (such as TiO2) is exposed to light with enough energy for its activation (in the case of TiO2, ultraviolet (UV) irradiation with wavelength < 388 nm). By using combined adsorption & TiO2 PCO filters, a synergetic effect can be achieved: i) PCO efficiency is improved, since the contact between the pollutants and the surface of the photocatalyst (where the reaction takes place) is increased by adsorption and ii) the adsorbent acquires a self-cleaning behaviour since adsorbed pollutants are removed by PCO, lengthening the life span of the filter.

The efficiency of BREEZE technology for the removal of VOCs, ozone, bacteria, and viruses has been assessed and optimised under simulated real conditions (high flow rate 300 L/s-, 23ºC and low humidity -15% relative humidity-), ensuring a lifespan above 3 000 flight hours (FH) by means of ageing tests.

How the BREEZE filtration process works
How the BREEZE filtration process works

 

If the BREEZE device with HEPA is compared with current technology (HEPA and standard activated carbon filter), BREEZE reduces the potential environmental impacts in all impact categories considered. Focusing on the climate change category, the reduction of the impact is 23% when both systems are compared. In conclusion, assuming that the superior lifetime can be taken advantage of, the BREEZE technology represents a better option in terms of environmental performance.

The project was coordinated by Leitat with Liebherr Aerospace as the topic leader. Leitat Technological Center was responsible for the development of the reactor, its life cycle analysis, economic assessment, and of the dissemination and communication of the results. The total EU funding for this project was € 708 347.50.