Investigation of design parameters in ultrasound milliflow reactors
KU Leuven Department Chemical Engineering Department of Industrial Science and Technology J. Jordens*, A. Honings, J. Degrève, L. Braeken, T. Van Gerven
* Corresponding author:
[email protected]
Introduction Flow reactors with ultrasound transducers attached to the walls appear to be very promising for application of sonochemical reactions [1-5]. For the first time, a 3D model is presented for simulation of the sonochemical degradation rate in such a reactor.
Methods Proposition of average cavity volume Case study: sonochemical degradation of CCl4 fraction (βav) as reaction independent Parameters studied: diameter & ultrasonic parameter to optimise reactor design: power
COMSOL Multiphysics model with 4 modules: 1) Pressure acoustics
𝛽𝑎𝑣 (%) = 100 ∙ 2) Acoustic pressure with bubble attenuation
3) Laminar flow
𝛽 𝑑𝑥𝑑𝑦𝑑𝑧 𝑑𝑥𝑑𝑦𝑑𝑧
CH4,Cl,ClCCl4
with β, the bubble volume fraction calculated as [6]: −9
𝛽 = 2. 10 . 𝑝
4) Sonochemical conversion
Ultrasound f: 20 kHz P: 30 W
0.018% Xi
0.016%
βav
0.014% 0.012% 0.010% 0.008% 0.006% 0.004% 0.002% 0.000%
0
2
4
6
8
10
12
14
16
1.4
Conversion per Watt (%/W)
110 100 90 80 70 60 50 40 30 20 10 0
Average cavity volume fraction [βav]
Improvement factor [Xi]
Results 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0
25
Graphical representation of acoustic pressure amplitude (Pa)
2 mm 4.9 mm
11 mm
0.1
0.2
75
100
125
150
175
200
225
Input power (W)
Diameter (mm)
0
50
0.3
0.4
0.5
Optimisation of diameter (4.9mm): •Highest conversion; •Highest acoustic pressures; •Highest value of βav. Optimisation of power (64 W): •Highest conversion per Watt of input power
0.568 MPa
Conclusion •Optimal diameter corresponds to highest acoustic pressures and highest average cavity volume fraction; •Moderate power level seems to be more efficient than elevated input powers; •Average cavity volume fraction seems to be good estimator for optimal reactor design. References
Acknowledgements:
[1] P.R. Gogate, V.S. Sutkar, A.B. Pandit, Sonochemical reactors: Important design and scale up considerations with a special emphasis on heterogeneous systems, Chemical Engineering Journal, 166 (2011) 1066-1082. [2] G. Ruecroft, D. Hipkiss, T. Ly, N. Maxted, P.W. Cains, Sonocrystallization: The Use of Ultrasound for Improved Industrial crystallization, Organic Process Research & Development, (2005) 923-932. [3] P.R. Gogate, Cavitational reactors for process intensification of chemical processing applications: a critical review, Chemical engineering and processing, 47 (2008) 515. [4] S. Lawton, G. Steele, P. Shering, L. Zhao, I. Laird, X.-W. Ni, Continuous Crystallization of Pharmaceuticals Using a Continuous Oscillatory Baffled Crystallizer, Organic Process Research & Development, 13 (2009) 1357-1363. [5] Y.-F. Su, H. Kim, S. Kovenklioglu, W.Y. Lee, Continuous nanoparticle production by microfluidic-based emulsion, mixing and crystallization, Journal of solid state chemistry, (2007) 2625-2629. [6] S. Dähnke, Modellierung sonochemischer Prozesse: Berechnung von Schallfeldern und Kavitationsblasenverteilungen, Buch- and Offsetdruckerei Günter Stubbemann GmbH, Hamburg, 1999
Research funded by a Ph.D. grant of the Agency for Innovation by Science and Technology (IWT).
