EFFECT OF PLASTIC MEDIA ON MASS TRANSFER AND BUBBLE HYDRODYNAMIC PARAMETERS IN BUBBLE COLUMN AND AIRLIFT REACTOR

Abstract

The objective of this work was to study and compare the mass transfer and bubble hydrodynamic parameters obtained with a bubble column reactor (BC) and internal loop airlift reactor (ILALR), as well as, analyze the effect of different types and amounts of plastic media presence in the reactors. More over the best reactor and plastic media (Type and concentration) observed in this work was applied for design the benzene absorption control system. The BC was made of Plexiglas with 14 cm in diameter and 100 cm in height. For an ILALR system, the rectangular Plexiglas baffle (with 13 cm width, 80 cm height, and 0.5 cm thickness) was installed within the BC in order to divide the cross section into a riser zone and a down-comer zone. Moreover, Polypropylene (PP), Poly Vinyl Chloride (PVC) and Acrylonitrile Butadiene Styrene (ABS) were applied as the plastic media with different concentrations of 2-15 %v/v. The mass transfer parameters (overall mass transfer coefficient; KLa and liquid-side mass transfer coefficient; KL) and the bubble hydrodynamic parameters (bubble size; DB, terminal bubble rising velocity; UB, and specific interfacial area; a) were determined for providing a better understanding on mass transfer mechanism. It can be noted that the KLa values were determined by using dissolved oxygen electrode; whereas the DB and UB values were determined by using a high speed camera (350 frames/sec) with an image analysis program. The result has shown that the KLa coefficients obtained with both reactors increased with gas flow rate (QG). The values of KLa in case of ILALR (0.89-3.47 min-1 and 0.91-3.48 min-1 for riser zone and down-comer zone, respectively) were greater than those in case of BCR (0.53 and 2.03 min-1). The gas (bubble) and liquid recirculation occurred in ILALR system can be defined as one of the important factors in this study. Moreover, the KLa coefficients can be clearly enhanced by adding the suitable type and concentration of plastic media (15 %v/v of PP): the modification of terminal bubble rising velocity and specific interfacial area should be responsible for these results. Finally, for benzene absorption, the highest benzene removal efficiency in this work was obtained with 15% of PP and 195 g Granular activated carbon (GAC) addition into tap water in the ILALR.