Microscale MassExchanger for Forward Osmosis Matthew Bertram Matthew
Microscale Mass-Exchanger for Forward Osmosis: Matthew Bertram, Matthew Cunningham June 2008 Osmosis Principles Microtechnology offers a number of potential benefits over conventional technologies. Forward osmosis microtechnology may: • Improve water transport • Improve system performance • Reduce membrane usage • Speed processing time 10 8 6 5 M 2. 5 M 1 M 4 2 0 0 1 2 3 4 Flow Rate (ml/min) 5 6 Model: Semi-permeable Membrane: (A) 0. 125 (B) (A)In micro technology, there is a limited bulk flow regime. Mass transfer is more efficient due to the limited transfer distance. (B)Conventional technologies have large bulk flow regimes that limit mass transfer. Experimental Device: 1 ml/min 0. 120 2 ml/min 0. 115 3 ml/min 0. 110 5 ml/min 0. 105 1 ml/min model 0. 100 2 ml/min model 0. 095 3 ml/min model 5 ml/min model 0. 090 The membrane functions by rejecting the salts (purple, green) while allowing water to pass through. Salts are rejected because of the “hydrosphere” of water molecules surrounding them. 0 Conclusions: 1 2 3 4 Draw Inlet Concentration (M) 5 6 • Observed flux in micro-featured device is three times higher than a macro-scale device • With the given testing space, water recovery ranges from 2% to 10% for a single pass. • Device permeability is estimated to be 373 g/(m 2 min) (L/mol) • Model shows promise for performance characterization, but more data is needed to become fully functional Forward and Reverse Osmosis Across a Membrane: (A) water naturally flows across the membrane from low concentration to high concentration. This is known as osmosis. (B) pressure is added to the concentrated side until water moves across the membrane to the dilute side. This is Reverse Osmosis. 12 Flow and Concentration Dynamics in Macro and Microtech: Osmosis or forward osmosis harnesses a difference in osmotic pressure to drive water across a semi permeable membrane from one solution to another. Analysis Raw Data: Brine Outlet Concentration (M) • Collect mass transfer data to compare micro-featured (channel depth ~ 100 um) performance to macro-featured (channel depth > 1000 um) • Characterize mass transfer rates in a prototype device • Develop a model to estimate intensive properties related to mass transfer phenomena Microtechnology Brine Water Recovery Percentage Objectives • microchanel device injected with green dye to highlight channel characteristics • Device arranged for crosscurrent flow with membrane sandwiched between channels. Special Thanks To • Mr. Todd Miller (ONAMI) for lab space, and guidance • Dr. Ed Beaudry (HTI) for expertise and membranes • Dr. Philip Harding for his guidance and mentorship • Dr. Alex Yokochi for technical advice and assistance • Dr. Goran Jovanovic for additional lab space
- Slides: 1