Numerical Simulation and Validation in Scrubber Wash Water Discharge from Ships

Abstract

A regulation on the sulfur emissions of ships sailing in global sea areas has been enforced since 1 January 2020. In this new regulation, ships are required to use low-sulfur fuel oils or to install an after-treatment equipment, such as a scrubber. Open and hybrid scrubbers wash the exhaust gas using seawater and then discharge the wash water overboard. According to the regulation promulgated by the International Maritime Organization (IMO) Marine Environment Protection Committee (MEPC), the wash water must have a pH of 6.5 or higher at 4 m from the discharge point. Wash water is generally acidic, with a pH of 2.5–3.5, whereas seawater is alkaline, with a pH of approximately 8.2. The wash water is dispersed after being discharged overboard through a nozzle, and its pH is restored through dilution with the surrounding seawater. In this study, the pH was calculated by using a theoretical chemical reaction model, and then the dispersion of wash water was analyzed using CFD simulation. This study describes the process of selecting the appropriate turbulent Schmidt number in a wide range of nozzle diameters. Finally, the appropriate nozzle diameter was determined based on the initial pH of the discharged scrubber wash.

Computational Fluid Dynamics Simulation Approach for Scrubber Wash Water pH Modelling

“…As stated within the introductory section of this article, based on the existing rules and regulations [13,16,17] and taking into account the available findings in the theoretical and practical studies and results [4,12], the maximum acceptable volume fraction of the scrubber wash water flow, at 4 m distance from the outlets, is deemed to be 0.47, for which the pH value of the diluted wash water is a minimum of 6.5.…”

“…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][5][6][7].…”

Improvement of the Cargo Fleet Vessels Power Plants Ecological Indexes by Development of the Exhaust Gas Systems

“…This system allows vessels to continue to use heavy fuel oil while still meeting the Tier II and III requirements for SO x emissions. However, the use of these scrubber systems necessitates the selection of scrubber elements, depending on the operating mode [15], and also causes problems in terms of the disposal of water from scrubber washing, especially when vessels are at sea [16].…”

Multi-Sensor-Based Hierarchical Detection and Tracking Method for Inland Waterway Ship Chimneys

“…The construction of the Yangtze River Economic Belt is one of the key strategies of the national cross-regional coordinated development, and both the "Yangtze River Protection" and the "Yangtze River Green Ecological Corridor" are the top priorities of the construction of the Yangtze River Economic Belt. The International Maritime Organization (IMO) has mandated a gradual reduction of nitrogen oxide and other types of gas emissions [1], and a regulation on sulfur emissions from ships sailing in global waters has been in effect since 1 January 2020 [2]. In addition, the design of ships' intake ports and the exhaust ports of the exhaust gas is being modified in accordance with the requirements of the International Maritime Organization (IMO) [3].…”