The full text of this item is not available at this time because the student has placed this item under an embargo for a period of time. The Libraries are not authorized to provide a copy of this work during the embargo period, even for Texas A&M users with NetID.
Modeling of Pressure Retarded Osmosis Using the Q-Electrolattice Equation of State
MetadataShow full item record
The mixing of solutions of different salinities occurs in many practical situations. A large-scale example is the mixing of river water with seawater. Such mixing processes have attracted much attention as a potential renewable energy source through a membrane-based process known as pressure-retarded osmosis (PRO). The ultimate goal of PRO units is to convert the energy released by the mixing process into mechanical or electrical power. While many researchers agree that PRO processes based on the salinity difference between freshwater and seawater are unfeasible at current conditions, more study is necessary to assess the feasibility of processes based on streams of higher salinity. One such processes is the energy recovery from desalination units by taking advantage of the mixing of discharged brine and seawater. Another process is the mixing of seawater with high-salinity produced water from oil exploration. This thesis investigates the power that can be harvested from different mixing systems such as freshwater+seawater, brine+seawater, and produced-water+seawater by PRO. To assess the performance of PRO, it is necessary to predict various thermodynamic properties such as Gibbs free energy, osmotic pressure, molar volume, entropy, and enthalpy and to calculate water fluxes across the membrane accurately. The Q-electrolattice equation of state (EOS), which extends a lattice-based fluid model for electrolyte solutions, is adopted to estimate the thermodynamic properties of the electrolyte solutions. However, the behavior of water fluxes through the membrane unit is much complicated due to concentration polarization, fouling of membrane, and reverse salt flux. Recently two very useful equations have been proposed to estimate the water and salt fluxes across the membrane that consider all of them, but the problem is the implementation of these equations into the PRO calculation. Many models have been developed for PRO calculation, which calculates thermodynamic properties, water flux, and power outputs separately even though they are interdependent, thus introducing the possibility of inconsistent results. In addition, quite often, studies on this topic adopt correlations for these various properties and are based on solutions of Na⁺ and Cl¯ ions only while, in practice, the solutions contain many other ions. This work develops a model to estimate the power recovery from the mixing of two solutions of different salinities by incorporating mass flux equations with Q-electrolattice EOS, which is capable of estimating all necessary thermodynamic properties and determining water and salt fluxes and power density simultaneously in a single framework. Initial investigations have been done for the solutions of Na⁺ and Cl¯ ions only. Finally, the developed model is extended to solutions of multiple ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl¯ and SO²¯₄) and to multiple membrane systems.
Rahman, Fahim-Bin-Abdur (2017). Modeling of Pressure Retarded Osmosis Using the Q-Electrolattice Equation of State. Master's thesis, Texas A & M University. Available electronically from