Jurnal Kejuruteraan 32(2) 2020: 239-246 https://doi.org/10.17576/jkukm-2020-32(2)-08 Simulation Study on Liquid Droplet Size Measurement inside Venturi Scrubber Nur Tantiyani Ali Othman a, b* & Simreth Kaur Dhalywala b a Research Centre for Sustainable Process Technology (CESPRO), Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia b Programme of Chemical Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia *Corresponding author: tantiyani@ukm.edu.my Received 24 May 2019, Received in revised form 28 January 2020 Accepted 25 February 2020, Available online 30 May 2020 ABSTRACT Droplet distribution is an importance factor to observe scrubber’s performance as uniform droplets distribution improved the particle’s collection efficiency at minimal liquid usage. Yet, the optimization problem typically involves complicated model functions to predict particle’s collection efficiency and pressure drop. Since the interaction between liquid droplets and gas phase is complex and difficult to solve by an experimental approach. Thus in this study, the prediction of liquid droplet’s behavior in the venturi scrubber was observed by using computational fluid dynamic. The liquid was injected through two orifices on the throat wall. The droplet size at different position was observed at various range of a gas velocity from 70 to 100 m/s and the ratio of liquid to gas of 0.07 to 2.0 L/m 3 to determine the optimum absorption rate. The droplet’s breakup in the venturi scrubber was observed using ANSYS © simulation where two-fluid model Eulerian-Eulerian approach was applied. It shows as the gas passes through the throat section, the velocity increases gradually and as it passes through the divergent section, it decreases causing the droplet diameter to increase. Typically, the gas velocity in the throat section is between 30-120 m/s, however in this simulation, the gas velocity of 70-105 m/s shown an adequate to achieve the optimum absorption rate. Besides, the liquid to gas ratio less than 0.06 was insufficient to cover the throat, and by increasing it up to 1.0 does not significantly improve the particle collection efficiency as the velocity at the scrubber’s throat drops which a larger droplets diameter was formed. Keywords: Droplet distribution; venturi scrubber; ANSYS © CFX; phase separation; gas velocity INTRODUCTION Micron-sized dust particles are known to have a fatal effect on human bodies, especially the heart and lungs. These fine particles are mainly generated from the internal combustion engines of cars or other motor vehicles, fuel burned at stationary sources for example power-generating plants, and numerous industrial processes. A lot of venturi scrubbers have been used in the industrial plants since 1940s, to remove the harmful particles and dust in the range of 0.5∼10 μm (Green Fact, 2001). Thus, the venturi scrubber has been widely used in the industry as a gas cleaning devices to control pollution emissions, due to high collection efficiency, simple structure, low cost and implementation (Ahmad and Talaie, 2010). In a venturi scrubber, the droplet distribution is an importance factor to observe the performance of a scrubber where a uniform droplets distribution can improve the particle’s collection efficiency at a minimal liquid usage. Yet, the optimization problem typically involves the complicated model functions, both operating and design parameters like gas velocity, liquid to gas ratio, throat’s length, nozzle’s diameter and throat aspect ratio (ratio of depth to width) in order to predict the particle’s collection efficiency and pressure drop (Pulley, 1997, Viswanathan, 1998, Mussatti, 2002 & Ravi et al., 2003). Since the interaction between the liquid droplets and gas phase is a complex problem and difficult to solve by experimental approach (Fernández et al., 2001), thus the prediction of a multiphase dynamic behavior in the industrial equipment with a computational fluid dynamics (CFD) has gain more attention (Guerra et al. 2012, Sharifi et al. 2013 & Othman et al. 2018). Therefore, in this study, a Pease-Anthony type of venturi scrubber was developed using ANSYS © software in order to observe a liquid droplet’s behavior and to determine the optimum absorption rate. Also, to ensure the CFD analysis is acceptable, this numerical simulation need to be verified with the experimental data in order to evaluate their feasibility.