Chemical Engineering and Processing 50 (2011) 1137–1142 Contents lists available at SciVerse ScienceDirect Chemical Engineering and Processing: Process Intensification jo u rn al hom epage: www.elsevier.com/locate/cep Experimental verification of the effect of liquid deposition on droplet size measured in a rectangular Venturi scrubber V.G. Guerra, J.A.S. Gonc ¸ alves ∗ , J.R. Coury Federal University of São Carlos, Department of Chemical Engineering, Via Washington Luiz, Km. 235, 13565-905, São Carlos, SP, Brazil a r t i c l e i n f o Article history: Received 15 September 2010 Received in revised form 30 March 2011 Accepted 10 September 2011 Available online 29 September 2011 Keywords: Venturi scrubber Droplet size Liquid film Film fraction Transversal injection Jet atomization a b s t r a c t It has been reported by previous studies [1–7] that droplet size in a Pease-Anthony Venturi scrubber depends on the jet atomization conditions, such as jet velocity and gas velocity. The assumption of this paper is that actual collector-droplet size in a confined tube such as the Venturi scrubber also depends significantly on preferential droplet deposition on the tube walls, which remove preferentially droplets of a certain size from the core, modifying the mean droplet size of the remaining droplets. To account for this effect, the present study is focused on the experimental measurement of the liquid deposition on the walls of a Pease-Anthony Venturi scrubber and the droplet size remaining in the core. The experiments were carried out varying jet penetration and the number of the injection orifices. A correlation, using dimensionless numbers, was proposed to quantify the influence of each experimental condition. The results showed that liquid deposition has a significant influence in actual collector-droplet size inside a Venturi scrubber. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The Venturi scrubber is widely used in industry to control par- ticle emission. It is comprised of three principal parts: convergent section, throat and divergent section. A cleaning liquid introduced into the scrubber removes the contaminants from the gas flow. Generally, the liquid is introduced through orifices in the throat of the scrubber as a jet. The high velocity of the gas developed in the throat of the equipment rapidly atomizes the liquid jets into numer- ous droplets. The droplets act as collectors of the particles contained in the gas and their size and distribution are important parameters for the efficient removal of contaminants and in the energy con- sumption of the operation [1–8]. Many factors affect the size of the droplets inside the Venturi scrubber, depending on the operat- ing conditions employed, such as: gas velocity, liquid velocity and the number of orifices used to inject the liquid [1]. Operating con- ditions can, favorably or unfavorably, affect phenomena such as: primary and secondary atomization, coalescence of droplets and the sizes of droplets deposited preferentially on the interior walls of the equipment, among others. During the process of atomization, not all the liquid introduced into the scrubber creates droplets that really act like particle collec- tors. A fraction of the liquid deposits on the walls of the equipment and flows as a film. The presence of the film affects the equipment’s ∗ Corresponding author. Tel.: +55 16 3351 8045; fax: +55 16 3351 8266. E-mail address: jasgon@ufscar.br (J.A.S. Gonc ¸ alves). collection performance, since it presents a smaller surface area than the droplets and can increase pressure drop, due to attrition between the gas and the wrinkled surface of the film. The fraction of liquid deposited on the equipment walls is strongly influenced by the distribution of liquid inside it; in turn, distribution is influenced by the penetration of the liquid jet inside the scrubber. Insufficient jet penetrations inside the throat tend to deposit liquid on the walls where the injection orifices are localized and excessive jet penetrations favor liquid deposition on the walls opposite to the injection orifices. Penetration by the jet is directly proportional to the velocity of the liquid and inversely proportional to the velocity of the gas. The empirical correlation developed by Viswanathan et al. [9] is widely used to predict the penetration of the jet into the interior of Venturi scrubbers: ℓ ∗∗ = 0.1145  l · V j  g · V g d o (1) in which V j = 4 · Q l  · d 2 o · N o (2) According to a study by Wu et al. [10] the rupture of a liq- uid jet, introduced into an orifice perpendicular to an air stream, happens through the formation of two main regions, as shown in Fig. 1: column breakup and surface breakup of the liquid. The col- umn breakup is located on the upper part of the jet and the surface breakup is located on the lower part of the jet. This suggests that jets with excessive penetration favor the deposition of the largest 0255-2701/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.cep.2011.09.005