(756d) Rigorous Process Simulation Using Reverse Osmosis (RO) Membrane Unit Operation for Water Desalination

OLI is the recognized leading provider of simulation software for electrolyte chemical systems, as well as for the prediction of corrosion. This USA-based company has served the chemical process and oilfield industries for over 48 years. OLI technology specializes in the rigorous prediction of multi-phase, multi-component chemical processes. Its temperature and pressure ranges are extreme (-60°C and 4000 bar), and the breadth of chemistry covered include 80+ elements, aqueous and non-aqueous organics, and their behavior in water, vapor, organic, solid, and interfacial environments. The combination of fundamental thermodynamics, property models, numerical algorithms, and databanks enable this unique capability. OLI has multiple thermodynamic models to cover this chemistry and phenomena.

This paper will present a novel scientific approach for process engineers to use while simulating and predicting the behavior of reverse osmosis membranes under various conditions. This approach is based on first-principles models to predict membrane permeability using simultaneous electrolyte thermodynamic models, species-transport models, chemical speciation, water coordination and ion hydration (and their respective radii). The paper will consist of three sections. In the first section, we will discuss the electrolyte modeling capabilities in process simulation. In the second section, we will discuss the theory behind RO membrane unit operation block. The third section will consist of a case study using the said RO membrane unit operation block.

This paper will illustrate the OLI Mixed Solvent Electrolyte thermodynamic model. Sample chemical systems will be potash, sulfuric acid and lithium double salts.

To model the transport mechanism inside the RO membrane, a solution-diffusion approach has been incorporated. In the solution-diffusion model, it is proposed that transfer of ions and water through polymeric membranes occurs via a solution diffusion mechanism because of dissolution of permeates in the membrane materials.

In the example case study, the simulation of a desalination plant located in Egypt will be considered with the goal of producing potable water with a TDS (total dissolved solids) less than 100 ppm reduced from a brackish feed water of over 10,000 ppm TDS.