(187c) Model-Guided Design of a Solar-Assisted Water Desalination Process through Membrane Distillation
AIChE Annual Meeting
2019
2019 AIChE Annual Meeting
Topical Conference: Next-Gen Manufacturing
Poster Session: Next-Gen Manufacturing
Monday, November 11, 2019 - 3:30pm to 5:00pm
Membrane distillation (MD) is an emerging technology for desalination of seawater and brackish water. MD is a thermal process in which the desalination occurs by diffusion of water vapor across a hydrophobic porous membrane in contact with hot saline/feed (e.g., 50-80 oC) and cold freshwater/distillate streams. In MD, the driving force for transmembrane vapor permeation is the difference between the saturation vapor pressure of water across the membrane. The operating pressure and temperature in MD process are very mild; this is the main advantages of MD over other commercialized water desalination technologies such as reverse osmosis (RO) and mechanical vapor compression (MVC). Hence, the MD process can be coupled with affordable energy sources such as solar energy or waste heat. Nonetheless, MD has not been fully commercialized mainly due to lack of proper design of material and devices (e.g., membrane modules) that makes the process relatively energy intensive. For this reason, we applied a model-guided approach to design a high-performance integrated solar-assisted hollow fiber membrane module. To do so, a three-dimensional (3D) multi-physics model of a hollow fiber membrane module was developed, and the effect of operating and design parameters on the module performance was investigated. The permeate flux and thermal efficiency of the system were considered as the characteristic parameters of the module. The simulation results indicated that the permeate flux for the module can be enhanced by 54% if the module is designed properly. In the next step, the results of our multi-physic simulations were used to write energy and mass balance around a solar-MD system. A set of ordinary differential equations (ODEs) was developed, and the influence of module and membrane parameters on the performance of the system was taken into consideration. Both design and processing conditions were searched to find an operational condition that allows for operating closer to the thermodynamic limits. To design and fabricate a Solar-MD system, the importance of a few key design parameters: module properties such as length, packing density, membrane properties, processing conditions such as flow rates, and system disturbance such as fluctuation in solar irradiance were evaluated.