Modeling of electrostatic spray in a venturi scrubber † HT Yang, 1 S Viswanathan, 1 W Balachandran 2 and MB Ray 1 * 1 Department of Chemical and Environmental Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576 2 Department of Manufacturing and Engineering Systems, Brunel University, Uxbridge, Middlesex UB8 3PH, UK Abstract: This paper summarizes the results of an investigation into the distribution of the droplets produced by electrostatic nozzles inside a Pease–Anthony venturi scrubber. The model simulates the flux distribution of charged droplets injected from an electrostatic nozzle in the scrubber under the combined influence of hydrodynamic and electric fields. The effects of operating parameters, such as gas velocity, diameter of the scrubbing droplets, charge-to-mass ratio and liquid-to-gas ratio, on the flux distribution of the water droplets in the throat of the scrubber are also investigated. The model takes into account initial liquid momentum, electric, hydrodynamic and gravitational forces, and eddy diffusion. The flux distribution of the scrubbing liquid in the presence of an electric field is much improved over a conventional scrubber, and the effect increases with the increase in charge-to-mass ratio. However, the effect of an electric field on the droplet flow pattern for small drops in a strong hydrodynamic field is negligible. Simulated results are in good agreement with the experimental data obtained in the laboratory. # 2003 Society of Chemical Industry Keywords: venturi scrubber; flux distribution; electric force; charge-to-mass ratio; droplet diameter NOTATION C d Drop concentration (kg m 3 ) D d Diameter of water drop (m) E Electric field intensity (V m 1 ) F Liquid flow rate (m 3 s 1 ) g Gravitational acceleration (m s 2 ) i c Spray convective current (A) p Dimensionless variable indicating the pressure of assistant air in nozzle, p = P air /10 5 Pa P air Pressure of assistant air in nozzle (Pa) Q Charge of the droplets (C) Q d Water drops strength (kg m 3 s 1 ) Q f Water film strength (kg m 3 s 1 ) Q s Water source strength (kg m 3 s 1 ) R c Induction-electrode inside cylinder radius (m) R j Liquid-jet radius (m) v d , v G Velocity of water droplet and the gas respectively (m s 1 ) v G,th Gas velocity in throat (m s 1 ) v x , v y Component of drop velocity in x and y direction (m s 1 ) V 0 Supply voltage (V) m G Viscosity of gas (air) (N m 1 ) r Space charge density (C m 3 ) r d , r G Density of liquid (water), density of gas (air) (kg m 3 )  q m Charge-to-mass ratio per drop (C kg 1 ) e 0 Permittivity constant of vacuum (F/m) e rG Relative dielectric constant of air, dimensionless INTRODUCTION Venturi scrubbers are widely used for the collection of particles from industrial exhausts because of their low equipment and maintenance costs combined with operational safety and high collection efficiency. However, venturi scrubbers tend to have a high operating cost, primarily due to energy consumption along with low collection efficiency for submicron- sized particles. In the past, electrostatic augmentation of venturi scrubbers was found to improve the collection of submicron-sized particles. 1 In these scrubbers, electrical forces are introduced in addition to the normal impaction and diffusional scrubbing mechanisms. This is done by imposing a high elec- trostatic charge onto the fine particulates before they enter the inlet of the venturi scrubbers. The force of mutual electrical attraction (Coulombic force) drives the particles towards the droplets. In some cases, the (Received 15 April 2002; revised version received 5 August 2002; accepted 22 August 2002) * Correspondence to: MB Ray, Department of Chemical and Environmental Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576 E-mail: cheraym@nus.edu.sg † Paper presented at the Process Innovation and Process Intensification Conference, 8–13 September 2002, Edinburgh, UK # 2003 Society of Chemical Industry. J Chem Technol Biotechnol 0268–2575/2003/$30.00 181 Journal of Chemical Technology and Biotechnology J Chem Technol Biotechnol 78:181–186 (online: 2003) DOI: 10.1002/jctb.730