An in-situ thermally regenerated air purifier for indoor formaldehyde removal

Formaldehyde is a common indoor pollutant that is an irritant and has been classified as carcinogen to humans. Adsorption technology is safe and stable and removes formaldehyde efficiently, but its short life span and low adsorption capacity limit its indoor application. To overcome these limitations, we propose an in-situ thermally regenerated air purifier (TRAP) which self-regenerates as needed. This purifier has four working modes: cleaning mode, regeneration mode, exhaust mode, and outdoor air in-take mode, all of which are operated by valve switching. We developed a real-scale TRAP prototype with activated carbon as adsorbent. The experimental testing showed that the regeneration ratios for formaldehyde of TRAP were greater than 90% during 5 cycles of adsorption-regeneration and that through the 5 cycles, there was no damage to the adsorption material as confirmed by scanning electron microscope (SEM) and Brunauer-Emmett-Teller (BET) tests. The total energy consumption by the prototype for purifying 1000 m³ indoor air was 0.26 kWh. This in-situ thermal-regeneration method can recover the purifier's adsorption ability through at least five cycles.