Reducing Maritime Emissions

Oil sludge, a complex water/oil emulsion with suspended solids, constitutes one of the main solid wastes. Because of its high concentration of petroleum hydrocarbons, it is regarded as a hazardous waste and poses a threat to the environment.

Some 80% of the pollution from ships is caused by the operational oil discharges into the sea, often made in violation of international rules. Oil sludge constitutes the majority of such discharges. The proposed project that is led by ENVOREM, in partnership with University of Brighton (UoB) and Liverpool John Moore University (LJMU), aims to develop a prototype green technology which cleans sludges and recovers entrained oil, that will be able to be installed on board of ships and/or in ports.

The working principles of the proposed technology are based on a number of physical fluidic processes being, sludge particle resuspension, cavitation, gravity driven oil-water separation and solid particle deposition. All these processes are quite complex, and they cannot be easily quantified experimentally due to their highly transient nature. Multiphase numerical modelling using Computational Fluid Dynamics (CFD) is therefore in most cases a vital tool for understanding and quantifying such complex fluidic processes.

The research team at UoB will employ multiphase CFD methods in order to predict the transient characteristics of (i) water vapourisation during induced mechanical cavitation, (ii) interface dynamics between separated water-oil phases and (iii) concentration fields of solid particles during sludge particle re-suspension and settling.

The overall work lasting 12 months from the start of the project constitutes a distinct Work Package, WP6, consisting of 4 different Tasks (T). T6.1, Month 1 (M1)-Month 2 (M2):

Literature review on the physical characteristics of sludges in the maritime industry defining ranges of oil/water/solids content as well as operating conditions and constituent properties.

This task will also include direct collaboration with the engineering team in ENVOREM and the two maritime industry consultants in order to define the preliminary subsystem characteristics in the proposed technology.

This stage will aid in the definition of the overall framework of numerical simulations that need to be performed for the design and optimisation of the corresponding of the involved modules (bilge water conditioning, pump and control, sludge processing, fuel extraction, bilge water treatment).

T6.2, M1-M3: This parallel task will involve the validation of the particular numerical solvers in OpenFOAM that will be used for the simulation-based design and optimisation of each sub-process, against literature available experimental data.

The proposed solvers are (i) cavitatingFoam, (ii) multiphaseInterFoam, and (iii) multiphaseEulerFoam [3]. Custom solvers based on these standard OpenFOAM solvers might be developed by the UoB team to overcome potential limitations for the particular applications.

T6.3, M2-M7: In this task the validated and benchmark versions of the numerical solvers are applied for a wide series of parametric numerical simulations aiming in the simulation-based design and optimisation of the aforementioned processes and the corresponding modules.

T6.4, M7-M12: Additional validation of the numerical predictions with measurements from the prototype tests conducted by ENVOREM in WP5 are performed. Then further parametric simulations are conducted, utilising the optimised module configurations in order to end up with a 1D simplified system-level model for the prediction of the optimal operating conditions for future applications of the proposed technology.