SunCHem: a 3 rd Generation Biofuel Technology to Produce Methane from Algae

Transcription

1 SunCHem: a 3 rd Generation Biofuel Technology to Produce Methane from Algae Martin Brandenberger* 1, Martin Schubert 1, Johannes Müller 1, Frédéric Vogel 1, Christian Ludwig 1,2, Samuel Stucki 1, Anca G. Haiduc 2, Rizlan Bernier-Latmani 2 1 Paul Scherrer Institut, Laboratory for Energy and Materials Cycles, 5232 Villigen PSI, Switzerland 2 Ecole Polytechnique Fédérale de Lausanne (EPFL), ENAC-ISTE, 1015 Lausanne, Switzerland November 17, th Discussion Forum LCA of Future Biofuels, Switzerland *martin.brandenberger@psi.ch Content Introduction SunChem process The technology behind the process PSI s catalytic hydrothermal SNG process Summary Conclusions 1

2 SunCHem: Green Gas Hors Sol SunCHem: Green Gas Hors Sol Nutrients, Water, CO 2 CO 2 + H 2 O + hν CH 2 O + O 2 2 CH 2 O CH 4 + CO 2 CO 2 H 2 O Photo- Bioreactor Hydrothermal Gasification CH 4 O 2 Chemicals Wet Biomass (algae) 2

3 feed type thermal efficiency (biomass to residence SNG) time τ technological readiness + Why Hydrothermal Gasification? Chemical conventional efficiency of anaerobic conventional digestiongasification hydrothermal vs. gasification water content in feedstock gasification methanation Wood, grass manure, household most wet types (w residues, sewage water < 15 %) (w water > 60 %) sludge % [1] % [2] % [3] (feed absolutely dry) < 1 min. good (PDU 1 MW SNG in Güssing 2008) high efficiency for dry biomass, close to commercialization low efficiency for wet biomass (< 8 wt % DM manure) 20 days [2] very good (commercially available) established, commercialized residues, low efficiency, plant size G. Schuster, G. Löffler, K. Weigl, H. Hofbauer, Bioresource Technology 2001, 77, [1] A. Duret et al., Journal of Cleaner Production. 13(15), 2005: p manure, wood < 10 min. RD (PDU planned 2010) full conversion, high efficiency, fertilizer byproduct technical barriers to be solved [2] Y. Yoshida et al., Biomass Bioenergy. 25(3), 2003: p. 257 [3] J. Luterbacher et al., Environ. Sci. Technol., 2008 (submitted). Why Microalgae? Corn Wheat straw Sugarcane Miscanthus Macroalgae Microalgae (PBR) Microalgae (open pond) Current realistic yields Annual area yield (dry tons/ha/yr) Source: Outputs from the EPOBIO project, cpl press, September

4 Photobioreactors GreenFuel Technologies (USA) Subitec (Germany) Algomed - IGV in Klötze (Germany) Why Methane? kw el kw th 1 kw el 2.5 kw th Already available and affordable today 138 g CO 2 /km (Gasoline: 169 g CO 2 /k 4

5 Working under pressure Enthalpy (kj/kg) p = 1 bar p = 300 bar p = 10 bar p = 250 bar T pc, 300 bar Temperature ( C) Supercritical water the greenest organic Hydrothermal solventrefers to conversions in pressurized water ( bar) at temperatures of ca C. 400 Pressure (bar) subcooled liquid Critical Point supercritical water superheated steam Temperature ( C) Good solubility of tar-like and oily compoun Supercritical water behaves like nonpolar solvent Reduced solubility of salts 5

6 Salt solubility in supercritical water T pc = 385 C Precipitation of Na 2 SO 4 from a 4 wt% solution on a hot finger. T solution = 356 C, p = 25 MPa Hodes, M. et al., JSCF 29 (2004) F. J. Armellini, PhD thesis, Dept. of Chem. Eng., MIT, 1993 PSI s catalytic hydrothermal SNG process Flue gas Algae slurry Preheat er (Heat recover y) High pressure slurry pump Salt separator superheat er Salt brine Cooler (Gasification Methanation) Gas fired burner CO 2 Phase PS separator A Water Air SNG (to the pipeline or gas engine, fuel cell, gas turbine) 6

7 Liquefaction of Spirulina platensis 380 C, 30 MPa, τ = 15 min. No catalyst Carbon gasification: 10% Yield: 0.02 g CH 4 /g algae(dry) Good liquefaction but only modest gasification. 2.5% Spirulina 97.5% Water PSI s catalytic hydrothermal SNG process Flue gas Algae slurry Preheat er (Heat recover y) High pressure slurry pump Salt separator superheat er Salt brine Cooler (Gasification Methanation) Gas fired burner CO 2 Phase PS separator A Water Air SNG (to the pipeline or gas engine, fuel cell, gas turbine) 7

8 Experimental Hydrothermal Lab-Scale Plant Feed Feed Inlet Salt separator Temperature T13 T13 (Fluid, fix) DipTube tube Effluent Upper Heating Heating Block block 1 Temperature T4 T4 Lower Heating Block block 2 Temperature T5 T5 Temperature T15 T15 Preheater Temperature T16 T16 Brine Effluent Moveable T14 Thermocouple (Fluid, movable) T21 Recovery of Salts from an Artificial Salt Mixture Composed of K 2 SO 4 and Na 2 CO 3 Pressure 300 bar V Feed 960 ml/h m Saltseparator (SA) ca. 2.6 g/min V114-K2SO4-Na2CO Aperture 1:5 (SA to V17) Salt Start C 430 C 470 C 500 C Salt Stop Water Start Conductivity [µs/cm] Salt concentration inlet feed T 13 = 342 C T 4 = 390 C T 5 = 390 C Sampling T 13 = 385 C T 4 = 430 C T 5 = 430 C Sampling T 13 = 407 C T 4 = 470 C T 5 = 470 C Salt concentration at salt separator Sampling T 13 = 416 C T 4 = 500 C T 5 = 500 C Salt concentration Salt separation starts of effluent Sampling T13 SA Medium top T4 SA Mantle top T5 SA Mantle bottom Time [h] Feed CM [us/cm] CM1 [us/cm] CM2 [us/cm] 8

9 PSI s catalytic hydrothermal SNG process Flue gas Algae slurry Preheat er (Heat recover y) High pressure slurry pump Salt separator superheat er Salt brine Cooler (Gasification Methanation) Gas fired burner CO 2 Phase PS separator A Water Air SNG (to the pipeline or gas engine, fuel cell, gas turbine) Gasification of Spirulina platensis Carbon gasification: 10% Yield: 0.02 g CH 4 /g algae (dry) No catalyst Good liquefaction but only modest gasification. 2.5% Spirulina 97.5% Water 400 C, 30 MPa, τ = 66 min. 2-3 mm Ru/C With catalyst Carbon gasification: 93% Yield: 0.26 g CH 4 /g algae(dry) 100% 80% 60% 40% 20% 6% 49% 43% H2 CO CO2 C3H8 C2H6 CH4 0% Product gas (dry) 9

10 PSI s catalytic hydrothermal SNG process Flue gas Algae slurry Preheat er (Heat recover y) High pressure slurry pump Salt separator superheat er Salt brine Cooler (Gasification Methanation) Gas fired burner CO 2 Phase PS separator A Water Air SNG (to the pipeline or gas engine, fuel cell, gas turbine) Summary Conclusions Processing microalgae as a wet slurry above water s critical point avoids drying. Algal biomass can be completely gasified to a methane-rich gas in supercritical water using a suitable catalyst conditions. In a continuous process, nutrient salts are separated before the catalytic reactor and can be recovered as concentrated brine. A closed bioenergy system based on microalgae and hydrothermal gasification is a promising concept for CO 2 mitigation and biomethane production. 10

11 Thank you very much! 11