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ABSTRACT
A novel air pulsed column plate internal featuring plates having concentric circular slots of fixed width (3 mm) is conceptualized, tested, and compared against standard sieve plate internal for counter-current two-phase flow. This new plate design (slotted plates) offers significant intensification in terms of specific interfacial area by as much as ~ 50% vis-à-vis standard sieve plates. The studies are carried out in a 3 inch diameter air pulsed column with tap water as the continuous phase and 30% (v/v) tributyl phosphate in dodecane as the dispersed phase. A high-speed imaging system is used to quantify the state of dispersion and obtain drop size distribution along with Sauter mean drop diameter. The effects of pulsing velocity, dispersed phase velocity and continuous phase velocity on dispersed phase holdup, drop size and consequentially specific interfacial area have been systematically studied for both internals. In all cases, slotted plates are characterized by generation of smaller drops and a higher holdup leading to significant improvement in specific interfacial area. Previously reported correlations for estimating dispersed phase holdup and Sauter mean diameter in pulsed sieve plate columns are found to be inadequate for slotted plate internals. Therefore, new correlations for prediction of holdup and drop diameter have been proposed for the new plate design.
Nomenclature
| A | = | Pulsing amplitude [m] |
| a | = | Specific interfacial area [1/m] |
| d | = | Drop diameter [m] |
| dslot | = | Slot width [m] |
| d32 | = | Sauter mean drop diameter [m] |
| f | = | Pulse frequency [1/s] |
| g | = | Acceleration due to gravity [m/s2] |
| h | = | Inter-plate spacing [m] |
| n | = | Number density of droplets of diameter d [-] |
| N | = | Number of droplets having diameter in the range of d+Δd/2 [-] |
| Ntot | = | Total number of droplets measured in the analysis [-] |
| Vd | = | Dispersed phase superficial flow velocity [m/s] |
| Vc | = | Continuous phase superficial flow velocity [m/s] |
| Greek letters | = | |
| ε | = | Fractional open area [-] |
| ρ | = | Density [kg/m3] |
| ϕ | = | Dispersed phase holdup [-] |
| µ | = | Viscosity [kg/m s] |
| σ | = | Interfacial tension [N/m] |
| Subscript | = | |
| c | = | Continuous phase |
| d | = | Dispersed phase |
Acknowledgments
The first author (AS) is thankful to the Department of Atomic Energy, India for providing fellowship under DDFS-Ph.D. scheme.
Disclosure statement
No potential conflict of interest was reported by the author(s).