Studies of VOCs removed from packed-bed absorber by experimental design methodology and analysis of variance

Abstract

Indoor air quality is affected by volatile organic compound (VOC) pollutants and these are often emitted by furniture and building materials. To enhance indoor air quality, removing VOCs from indoor environment is an important task. Triethylene glycol (TEG) solution was used as working solution to absorb VOCs from ambient air in this study. Plastic 5/8 in. polaring-type was packed in the packed-bed absorber, and the packed length was about 34 cm. Toluene, methanol, ethyl ether, and methyl-ethyl ketone were absorbed separately by TEG solution. Two-level factorial experimental design methodology was applied to schedule the operating variables in the experiment. The advantage of experimental design methodology is to obtain reasonable experimental results with fewer experimental runs. In addition, the analysis of variance (ANOVA) was used to analyze the effect of operating variables (factors) on mass transfer coefficient (response). The p-value was used to assess the mass transfer performance of VOCs absorbed by packed-bed absorber. From experimental results, effect of air flux on mass transfer coefficient was significant except for methanol because the p-values were smaller than 0.1 for toluene, ethyl ether, and ketone. For VOCs concentration, the effect of methanol concentration on mass transfer coefficient was extremely significant; the effect of concentration of ethyl ether was very significant; the effect of concentration of toluene was significant; the effect of methyl-ethyl ketone was insignificant. Since all the p-values were smaller than 0.01 for liquid flux, the effect of liquid flux on mass transfer coefficient was very significant. By analyzing the factorial interaction, the factorial couples, toluene concentration × liquid flux, TEG concentration × methanol concentration, TEG concentration × ethyl ether concentration, and ketone concentration × liquid flux can be chosen as main variables to operate the absorption system for absorption of toluene, methanol, ethyl ether, and ketone to acquire the desired mass transfer coefficient.