(V08BT09A014)REMOVAL MECHANISMS OF SUSPENDED PARTICULATE MATTER IN HUMIDITY SWING AIR CLEANING METHOD

摘要

We are studying the removal of the SPM by a humidity swing method, in which sample air is consecutively humidified with heating and dehumidified with cooling. First, the removal effect of this method was experimentally demonstrated. The sample air was humidified to saturated moist air up to 66°C and then cooled to 13°C. The results showed the decrease of the SPM concentration. The SPM survival ratio is plotted against the drop of absolute humidity through the dehumidification; and the survival ratio exponentially decreased to ~0.2. Also, the dependence of removal characteristic on SPM concentration was not shown for 10 ~ 10000 particles/cc. Also, growth of SPM due to nuclear condensation was observed in the experiments. However, the number of SPM grown to several micrometers where SPM significantly decreases with gravity was very small. Therefore gravitational sedimentation would not be enhanced. Next, SPM transfer in the dehumidifier was calculated. The heat and mass transfer through the dehumidifier was calculated; and then, variation of SPM concentration by suction flow and themophpresis were obtained. The analysis of SPM transfer showed that the dominant phenomenon for SPM transport in the dehumidifier is suction flow. However, the calculation considering thermophoresis and suction flow predicted the removal effects several times lower than the experiments. Thus, the removal mechanism of the humidity swing method should be explained by unidentified phenomena.