Utilization of PU Foam Insulation Waste to Air Purifier Filter

Abstract

    In 2017, Thailand’s electronic waste production reached 0.4 million which included refrigerator waste. Refrigerators that are no longer required are sorted and separated to recycle valued parts, while over 20,000 m³ of rigid polyurethane (PU) insulating foam is discarded in community dumping sites or illegally burned. This research aimed to add value to the PU foam waste by adopting it as an air purifier. Thus, we designed and constructed a prototype of a portable air purifier embedding a filter to trap PM_2.5 made from PU foam. Our designed 36x36x78-cm³ air purifier was made from aluminum and covered with galvanized iron flat sheet. It was equipped with a 220-W centrifugal fan and griller tower to distribute dirty air evenly. An air filter cartridge was a 31x5x44-cm³ aluminum frame filling with three individual PU foam shapes, including stripe, cubic and ball. We evaluated the air purifier performance, in terms of a clean air delivery rate (CADR) for removal of PM_2.5. Test particles were generated by burning an incense stick in an 8-m³ test chamber to achieve an initial concentration of 250 µg/m³. CADRs were determined by fitting 1.5-h concentration profiles to mass balance models, using nonlinear regression. At the end of testing, the PM_2.5 concentrations were as low as 3-43 µg/m³. The CADRs for the stripe, cubic and ball shapes were 14.3, 18.6 and 21.3 m³/h, respectively. The ball-shape filter exhibited the similar CADR to the 35-Watt HEPA commercial air purifier. An additional prefilter sheet helped to increase the CADRs for all PU foam filter shapes by 50-90%. The production cost is 5,000 baht. It is noteworthy that the expired PU foam air filter can be ultimately used as an aggregate for lightweight concrete