Citation: Ristea, M.; Popa, A.; Scurtu, I.C. Computational Fluid Dynamics Simulation Approach for Scrubber Wash Water pH Modelling. Energies 2022, 15, 5140. https:// doi.org/10.3390/en15145140 Academic Editors: Tadeusz Dziubak, Karczewski Miroslaw and Piotr Wróblewski Received: 29 May 2022 Accepted: 13 July 2022 Published: 15 July 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). energies Article Computational Fluid Dynamics Simulation Approach for Scrubber Wash Water pH Modelling Marian Ristea 1 , Adrian Popa 2, * and Ionut Cristian Scurtu 2 1 Jalmare Oy, 20500 Turku, Finland; marian.ristea@jalmare.com 2 Mircea cel Batran Naval Academy, 900218 Constanta, Romania; ionut.scurtu@anmb.ro * Correspondence: adrian.popa@anmb.ro Abstract: In the current article, we will use a CFD approach for the scrubber wash water dilution simulation, by considering the current MEPC (Marine Environment Protection Committee, a sub- sidiary of IMO—International Maritime Organization) regulations that are in force. The necessity for scrubber wash water pH modelling and its importance in the current environmental framework is emphasized. The presented 3D model is considered as a 400 mm hydraulic diameter fluid domain with two outlets and a discharge water flow rate of 3050 m 3 /h for the considered pH value of 3, obtained within a state-of-the-art exhaust gas scrubber solution developed by a major EGCS (Exhaust Gas Cleaning Systems) supplier. The CFD study was developed by considering a k-ε turbulence model. In order to achieve accurate results, a structured mesh with two levels of refinement volumes was realized. Based on the obtained data and the various parameters discussed, the paper presents a way to investigate the optimal results for further analytical research of the scrubber washwater dilution process within the exhaust gas cleaning system. Keywords: CFD; scrubber; wash water; pH modelling 1. Introduction Within the shipping industry, large quantities of fossil fuels are burned by the ship’s diesel engines, with the exhaust gases having carbon oxides (CO x ) and water (H 2 O) as the main components. Together with the main fractions [1–3], the combustion process also generates sulfur oxides (SO x ), nitrogen oxides (NO x ), and carbon-based matter (soot, smoke), all of them with huge environmental impact, such as acid rain and carbon-based airborne particles, which are detrimental to human health. Based on the real global concern about environmental issues, determined by the exhaust gas emissions and their impact, there is a huge interest in developing technical solutions for reducing the level of pollution [4–7]. Therefore, for both new builds and existing ships, a fitting/retrofitting race is ongoing—increasingly ships are using various solutions for cleaning the exhaust gases. A scrubber technology was developed with unique features to enable a more sustainable operating environment for the shipping industry [8]. The main objective of this study is to evaluate the open-loop solution, with an emphasis on the aspects regulated within MEPC 259(68). The open-loop cleaning process is based on exhaust gases “washing” with seawater, thus resulting in large quantities of residuals—sulfuric acid (H 2 SO 4 ) or sulfurous acid (H 2 SO 3 ) diluted in the wash water. The obtained product is seawater with increased acidity, which is to be discharged overboard (either treated in a second stage or diluted). 2. Study Aim, Materials and Methods 2.1. Marine Environment and Seawater Alkalinity The wash water with low pH values reacts with the salt in the seawater, forming carbonic acid, which is considered to be unharmful for the marine environment. The main Energies 2022, 15, 5140. https://doi.org/10.3390/en15145140 https://www.mdpi.com/journal/energies