Membrane contactors for efficient solvent regeneration.

Transcription

1 Membrane contactors for efficient solvent regeneration. Colin Scholes 1, Sandra Kentish 1, Geoffrey Stevens 1 and David demontigny 2 1 Department of Chemical Engineering, The University of Melbourne, Australia 2 Faculty of Engineering and Applied Science, University of Regina, Canada

2 Hybrid Technology Takes advantages of both membrane and solvent technology Solvent high selectivity for CO 2 Membrane controlled flow regimes Greatest advantage: achieves much higher active area per unit volume than traditional solvent columns significant reduction in size of CO 2 capture plant.

3 Desorption of CO 2 from solvent Pure CO 2 CO 2 rich solvent CO 2 CO 2 lean solvent 1 K = 1 k g + 1 k ps + 1 k m + 1 mek l Additional challenges solvent is at very high temperatures.

4 Composite Non-Porous Membranes Non-porous thin layer 12 to 15 µm on porous PP support. Three Glassy Polymeric Membranes used for the thin layer Poly (1-trimethylsilyl-1-propyne) (PTMSP), Polymer of Intrinsic Microporosity (PIM-1) and Teflon AF1600

5 PTMSP on PP contactor CO 2 flux and therefore overall mass transfer coefficient through the contactor dependent on temperature and solvent Reynolds number. Higher temperate increasing the diffusivity of CO 2 through the membrane, while higher Reynolds number increases turbulence in the solvent layer. Achieve good CO 2 mass transfer at temperatures below the boiling point of the solvent. Potential to avoid the latent heat of vaporization = low energy duty. Solvent: 30 wt% MEA

6 PIM-1 and Teflon AF1600 contactors PIM-1 Teflon AF1600 Similar overall mass transfer coefficients across the membranes with temperature. (Teflon AF1600 is lower because of lower CO 2 permeability) Solvent Boundary layer accounts for >90% of the mass transfer resistance. Similar to the absorption process.

7 Above the boiling temperature Asymmetric Composite Poly dimethylsiloxane (PDMS) membrane contactor Vapour on the feed side CO 2 Flux increases by an order of magnitude when the solvent is vaporized complete liberation of CO 2 from the carbamate species. Solvent: 30 wt% MEA

8 PDMS Mass transfer and CO 2 permeability Gas separation measurements Contactor measurements Overall mass transfer increase by over an order of magnitude above boiling temperature. Calculate CO 2 permeability in PDMS from mass transfer theory similar behavior to that observed in gas separation measurements.

9 Steam flux through the contactor PDMS Contactor The high temperature also produces a high water vapour pressure results in very high water fluxes across the membrane contactor. All have selectivity for H 2 O/CO 2.

10 Membrane Distillation configuration Flat sheet : Air Gap CO 2 Condensing water vapor is used to heat the CO 2 - rich solvent: ensures latent heat of evaporation is not lost. More energy efficient. PDMS composite membranes in a flat sheet membrane distillation approach.

11 Development of a Combined Process Pilot Plant at Vales Point coal-fired power station (NSW) Demonstrating both CO 2 absorption and CO 2 desorption through membrane contactors. Utilising commercially available membrane contactors with a range of commercial solvents.

12 Conclusion Membrane Contactors have the potential to revolutionize CO 2 Capture. Able to achieve CO 2 overall mass transfer coefficients greater than solvent absorption. Excellent mass transfer obtained for CO 2 desorption from a solvent. Solvent boundary layer dominates mass transfer resistance. For Desorption, high water flux is an issue and the need to minimise water loss from the solvent and reduce downstream condenser duty. Desorption configuration will be critical in reducing energy duty and optimizing the process.

13 Acknowledgements University of Melbourne Prof. Geoff Stevens Prof. Sandra Kentish Dr Kathryn Smith Dr Michael Simioni Dr Sang Lee Dr Shinji Kanehashi Dr George Chen Hirra Azher Hiep Lu Wen Tao Alita Aguiar University of Regina Dr David demontigny University of Auckland Dr Jiang Jin CO2CRC Dr Abdul Qader