Supercritical water gasification of macroalgae

Transcription

1 School of something School of Process Environmental and Materials Engineering ENERGY RESEARCH INSTITUTE FACULTY OF OTHER Supercritical water gasification of macroalgae Ramzi Cherad Jude A. Onwudili, Amanda R. Lea-Langton, Andrew B. Ross, Paul T. Williams Conference and workshop on cultivation and utilization of

2 Supercritical water gasification (SCWG) of macroalgae Introduction Supercritical Water Gasification (SCWG) Experimental Materials and Set-up Results Mass balance, hold time Seasonal variation, catalyst Process Water Conclusions and Further Work

3 Thermochemical processing of macroalgae Challenges of thermal conversion High moisture content (up to 90wt%). Ash High ash content (up to 50 wt%) High Halogen content Low heating value (10-15 MJ kg -1 ) Both combustion and pyrolysis require dry feedstock Protein Lipids Carbohydrate Typical Kelp composition (L. digitata) dry basis (Black 1950) Hydrothermal conversion routes more suited Tolerates high moisture content Tolerates high ash content Produces biochar, biocrude, or syngas

4 Supercritical Water Gasification Water - cheap, abundant, environmentally safe Supercritical water: Density Dielectric constant Role in reaction Critical Point = 374 C, 22.1 MPa

5 Supercritical Water Gasification Advantages Non-polar solvent High diffusivity and transport properties Varying properties allows altering temperature and pressure to tune reaction medium properties to optimal conditions for given chemical transformation High reaction rates give gas products with high concentrations Reactions proceed quickly and completely due to no limit of interphase mass transfer resistance

6 Supercritical water gasification (SCWG) of macroalgae Introduction Supercritical Water Gasification (SCWG) Experiment Materials and Set-up Results Mass balance, hold time Seasonal variation, catalyst Process Water Conclusions and Further Work

7 Materials Saccharina latisima Spring, summer, autumn and winter samples from harvests collected off the Scottish coasts of Barnacarry and Clachan Sound Catalyst 5% Ru / Al 2 O 3

8 Experimental Set-up Gasification Temperature 500 ºC Pressure bar Algae 1.0 g Water 15 ml Ru/Al 2 O g Hold time 0, 30, 60 min

9 Product analysis Gas Offline gas chromatography (GC) analysis Hydrocarbon gases (CH 4 and C 2 -C 4 ) GC fitted with flame ionisation detector (Varian C-3380 GC-FID) Permanent gases (H 2, N 2, O 2, CO, CO 2 ) GC fitted with thermal conductivity detectors (GC-TCD) Process Water Total organic carbon, ion chromatography, trace metal concentrations, phenols, total nitrogen Catalyst High resolution scanning electron microscope (SEM) coupled to an Energy Dispersive X-ray Sectrometer (EDXS)

10 Supercritical water gasification (SCWG) of macroalgae Introduction Supercritical Water Gasification (SCWG) Experiment Materials and Set-up Results Mass balance, hold time Seasonal variation, catalyst Process Water Conclusions and Further Work

11 Wt% Contribution Typical mass balance - SCWG of S. latisima Gas composition varies depending on residence time Non-catalysed Catalysed Rich in nutrients, can be recycled for microalgae cultivation 20 0 Gas Oil Residue WSP Products

12 Gas yield (mol %) CV (MJ/m 3 ) SCWG of S. latisima Hydrogen Carbon monoxide Methane C2-C4 Carbon dioxide CV min 30min 60min Hold Time 0

13 Supercritical water gasification (SCWG) of macroalgae Introduction Supercritical Water Gasification (SCWG) Experiment Materials and Set-up Results Mass balance, hold time Seasonal variation, catalyst Process Water Conclusions and Further Work

14 Seasonal variation Saccharina latisima Harvest site Harvest Moisture Ash C H N S O* CV (MJ/kg) Clachan Sound January Barnacarry April Barnacarry July Clachan Sound October *O by difference

15 Gas yield (vol %) CV (MJ/m 3 ) Seasonal Variation SCWG of S. latisima 40 Hydrogen Carbon monoxide Methane C2-C4 CV January 2009 April 2009 July 2009 October 2008 Harvest Month 8

16 Gas Yield (mol %) Gasification efficiency (%) Catalysed SCWG of S. latisima Hydrogen Methane C2-C4 Carbon monoxide GE

17 Used (4x) Fresh Catalysed SCWG of S. latisima

18 Supercritical water gasification (SCWG) of macroalgae Introduction Supercritical Water Gasification (SCWG) Experiment Materials and Set-up Results Mass balance, hold time Seasonal variation, catalyst Process Water Conclusions and Further Work

19 SCWG Process Water Process Water Low in phenols High in: Acetate ( ppm) Potassium ( ppm) Sodium ( ppm) Ammonium ( ppm) Sulphate ( ppm) Further work on the use of process water for microalgae cultivation to test suitability of nutrient recycling from SCWG

20 Supercritical water gasification (SCWG) of macroalgae Introduction Supercritical Water Gasification (SCWG) Experiment Materials and Set-up Results Mass balance, hold time Seasonal variation, catalyst Process Water Conclusions and Further Work

21 Conclusions - SCWG of macroalgae Macroalgae can be gasified successfully in SCW with a product gas consisting of H 2, CO, CH 4, CO 2 and small amounts of C 2 -C 4. High carbohydrate feedstock highly suitable for SCWG Yield of combustible gases from S. latisima increased to 60% of the product gas in the presence of ruthenium catalyst Process water rich in nutrients suggesting suitability for nutrient recycling for microalgae cultivation Further work needed on catalyst selection due to macroalgae s high sulphur and alkali metal content

22 Acknowledgments Dr. Jude Onwudili Dr. Amanda Lea-Langton Dr. Andrew Ross Professor Paul Williams

23 Thank you for your attention!