Influence of Bio-Syngas Contaminants on SOFC BioCellus & Green Fuel Cell Bert Rietveld, Nico Dekker, Jan Pieter Ouweltjes www.ecn.nl
Introduction A Solid Oxide Fuel Cell converts H 2 directly in electricity and heat - Electrochemical conversion: high electrical efficiency - No combustion: no NO x production O 2 (air) cathode 4e electrolyte anode 2O 2-4e 4e V: 0.7-1 V; T: 700-1000 C 2H 2 2H 2 O CO + H 2 O CO 2 + H 2 Overall: 2 H 2 + O 2 2 H 2 O + P el + Q heat CH 4 + H 2 O CO + 3 H 2 2 Fuel Quality Workshop
Introduction ESC (Electrolyte Supported Cell) ASC (Anode Supported Cell) electrolyte anode Cathode LSM/8YSZ (25-50 μm) Electrolyte 3YSZ (150 μm) Anode Ni/GDC (25-50 μm) LSCF 8YSZ Ni/8YSZ (25-50 μm) (5-10 μm) (550 μm) Temp 800-1000 C 700-800 C 3 Fuel Quality Workshop
Introduction Biocellus (EU, FP6) - Focus on Electrolyte Supported Cells (ESC) - Single cell tests with synthetic fuels and real bio-syngas - SOFC stack tests with bio-syngas, HT gas cleaning and thermal integration of Gasifier/SOFC GreenFuelCell (EU, FP6) - Electrolyte Supported Cells and Anode Supported Cells (ASC) - Single cell tests with synthetic fuels - SOFC stack test with bio-syngas and MT or HT gas cleaning 4 Fuel Quality Workshop
Approach Investigate the performance of the SOFC in relation to the organic compounds in the feed gas - Single cell tests with synthetic fuels (GreenFuelCell) - Single cell tests with syngas from gasifier (Biocellus) Determination of the allowable concentrations Stacktest with sufficiently cleaned gas from gasifier (GreenFuelCell + Biocellus) This presentation: Highlights investigation on electrolyte supported cells with Ni-GDC anode 5 Fuel Quality Workshop
Contaminants in bio-syngas Inorganic contaminants - H 2 S, COS, HCl = cleaning required! - NH 3 = fuel! Organic compounds: impact on SOFC unknown - CH 4 - C 2 H 2, C 2 H 4 - Tars: C 6 H 6 C 16 H 10 C 16 H 10 C 14 H 10 C 6 H 6 C 10 H 8 6 Fuel Quality Workshop
Typical bio-syngas composition Component Content Units CO 16 vol% CO 2 14 vol% H 2 14 vol% H 2 O 13 vol% N 2 36 vol% CH 4 4 vol% Acetylene 0.1 vol% Ethylene 1.4 vol% Toluene 0.4 vol% Naphthalene 525 vppm Phenanthrene 126 vppm Pyrene 22 vppm Main compounds C 2 H 2 / C 2 H 4 = C 2 H y C 7 H 8 C 10 H 8 C 14 H 10 C 16 H 10 7 Fuel Quality Workshop
In case of complete conversion: CH 4 + H 2 O CO + 3 H 2 C 2 H 2 + 2 H 2 O 2 CO + 3 H 2 C 2 H 4 + 2 H 2 O 2 CO + 4 H 2 C 7 H 8 + 7 H 2 O 7 CO + 11 H 2 C 10 H 8 + 10 H 2 O 10 CO + 14 H 2 C 14 H 10 + 14 H 2 O 14 CO + 19 H 2 C 16 H 10 + 16 H 2 O 16 CO + 21 H 2 Contribution to the fuel 25 % 1 % 13 % 11 % 2 % 0.7 % 0.1 % 8 Fuel Quality Workshop
In case of insufficient conversion: Graphitic carbon Encapsulating carbon Filamentous carbon Whisker-like carbon Pyrolytic carbon 9 Fuel Quality Workshop
Carbon formation catalyzed by nickel adsorption dehydrogenation hydrocarbon ad-species atomic carbon reaction + desorption polymerization dissolution no carbon graphitic carbon clustering encapsulated carbon dissolved carbon LT HT whiskers filaments 10 Fuel Quality Workshop
Pyrolytic carbon Mechanism: - nickel catalyses cracking of C-C bonds free radicals - polymerization of free radicals - deposition on catalyst support pore blocking When occurring: - unsaturated hydrocarbons, e.g. alkenes, aromatics - undiluted feed stream - high temperature (typically > 600 C) in gasifier 11 Fuel Quality Workshop
Single cell test-rig for synthetic fuels Temperature controllers of the evaporators, tubes and SOFC Gas flow controllers SOFC in oven Current control of the SOFC A/D converters for the Data Acquisition System Evaporators for H 2 O, toluene, naphtalene, phenantrene and pyrene Mass flow controllers 12 Fuel Quality Workshop
Gas infrastructure Anode MFC C 2 H y (N 2 ) H 2 S (H 2 ) CO 2 Cathode MFC SOFC in oven CO N 2 O 2 N 2 cathode anode H 2 GC CH 4 H 2 O SPA SPA N 2 -tolu. C 7 H 8 SPA N 2 -naph. N 2 -phen. C 10 H 8 SPA De-humidifier C 14 H 10 SPA N 2 -pyr. C 16 H 10 13 Fuel Quality Workshop
Test rig: humidifiers (naphthalene) 14 Fuel Quality Workshop
Electrical efficiency (ESC) with clean bio-syngas 1.0 0.9 ESC (850 C) 100% 90% Cell voltage (V) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 Cell voltage Fuel utilisation Efficiency 80% 70% 60% 50% 40% 30% 20% Fuel utilisation (%); Efficiency (%) 0.1 10% 0.0 0% 0.00 0.05 0.10 0.15 0.20 0.25 Current density (A/cm²) Fuel utilisation = Fuel converted / Input Fuel Efficiency = Electricity Produced / Energy Input (LHV) 15 Fuel Quality Workshop
Impact of C 2 H y and C 7 H 8 on the ESC cell voltage 900 ESC CKS5E060320-1 (850 C, 0.16 A/cm², U f =60%) ET 01-24 C 2 H 2 /C 2 H 4 C 7 H 8 0.1% C 2 H 2 850 1.4% C 2 H 4 800 0.4% C 7 H 8 V (mv) 750 700 650 300 310 320 330 340 350 360 370 380 390 400 Time (hours) Acetylene, ethylene and toluene act as fuel 16 Fuel Quality Workshop
Impact of C 14 H 10 and C 16 H 10 on the ESC cell voltage 900 850 ESC CKS5E060320-1 (850 C, 0.16 A/cm², U f =60%) C 14 H 10-126 ppm C 16 H 10-22 ppm ET 01-24 800 V (mv) 750 700 650 360 380 400 420 440 460 480 500 Time (hours) Deactivation by phenanthrene and pyrene 17 Fuel Quality Workshop
Impact of C 10 H 8 on the ESC cell voltage 900 ESC CKS5E060320-1 (850 C, 0.16 A/cm², U f =60%) ET 01-24 850 C 10 H 8-50 100 250 525 ppm 800 V (mv) 750 700 650 460 480 500 520 540 560 580 600 Time (hours) Deactivation by naphthalene 18 Fuel Quality Workshop
Impact of naphthalene on methane conversion 16.0 14.0 ESC (850 C, 0.16 A/cm²,Uf =60%) C 10 H 8-250 ppm GC data ET 01-24 Outlet concentration (dry, %) 12.0 10.0 8.0 6.0 4.0 H 2 CO 2.0 CH 4 0.0 520 525 530 535 540 545 550 555 560 Time (hours) Higher tars inhibit the methane reforming 19 Fuel Quality Workshop
Effect of C 10 H 8 on the cell performance: H 2 as fuel 900 ESC (850 C, 0.14 A/cm²,Uf =53%) CKS5E060320-1 ET 01-24 Reference gas: H 2 850 H 2 C 10 H 8-1050 ppm 800 V (mv) 750 I (A/cm 2 ) 700 650 1180 1190 1200 1210 1220 1230 1240 Time (hours) Slight effect of heavy tars on the electrochemical conversion of H 2 20 Fuel Quality Workshop
Single cell test-rig for real bio-syngas Heated duct for hot syngas 21 Fuel Quality Workshop
Single cell test-rig for real bio-syngas Gas conditioning unit Particle removal Chlorine removal Sulphur removal Tar pre-reformer + bypass Steam injector Trace heating to prevent tar condensation 22 Fuel Quality Workshop
Bio-syngas composition at test locations 23 Fuel Quality Workshop
Results testing day 1 at TUDelft, low U f Tars pre-reformed Tars > 10 g.m -3 No deactivation due to tars 24 Fuel Quality Workshop
Results testing day 2 at TUDelft, low U f Tars > 10 g.m -3 No deactivation due to tars 25 Fuel Quality Workshop
Post test analysis TU Delft cell No traces of carbon species 26 Fuel Quality Workshop
Stack test: Configuration at ECN BCE 1 : gasifier and cleaning SOFC: stack test Staxera stack Milena - gasifier TREC tar removal HGF - filter Gasification and cleaning Catalytic reactors SOFC stack test 1 Biomass, Coal & Environmental Research 27 Fuel Quality Workshop
Gasifier and Hot Temperature gas cleaning ECN-Milena gasifier - Air blown bubbling fluidized bed gasifier (feed: 4.2 kg wood/hour) Milena - gasifier 28 Fuel Quality Workshop
Gasifier and Hot Temperature gas cleaning ECN-TREC catalytic tar reduction reactor (olivine) - Operating temperature: 900 C, tar dew point <80 C TREC tar removal 29 Fuel Quality Workshop
Gasifier and Hot Temperature gas cleaning Ceramic filter - removal of particles HGF - filter 30 Fuel Quality Workshop
Gasifier and Hot Temperature gas cleaning HDS fixed bed reactor - Conversion of organic sulphur compounds to H 2 S. Fixed bed reactors for removal of sulphur and chlorine 31 Fuel Quality Workshop
Gasifier and Hot Temperature gas cleaning Catalytic reactors for hydrogenation and reforming of unsaturated and aromatic hydrocarbons Catalytic reactors 32 Fuel Quality Workshop
Stack test Staxera stack (MK-100) - 30 cells - Active area: 81 cm²/cell - ESC - Temperature: 800-850 C - Nominal output (H 2 /N 2 ): - 25 Volt at 10A (U f = 53%) 33 Fuel Quality Workshop
Stacktest: GFC (gasification) & SN (pyrolysis) 40 35 SN1, GFC1, GFC2: Beechwood; SN2: Rofire; SN3: waste of carpet industry SN1 SN2 GFC1 GFC2 SN3 Vcell (V), Current (A) 30 25 20 15 10 I Vstack 5 0 0 500 1000 1500 2000 2500 3000 3500 Time (hour) Total operating time 5500 hours, degradation of 1%/1000 hours 34 Fuel Quality Workshop
Stacktest: GFC (first 100 hours) Cell voltage in time (10 A) GFC-1 30 syngas H 2 /N 2 Gasifier: Beechwood H 2 /N 2 25 V1 Vcell (V) 20 15 10 5 V2 V3 V4 V5 V6 V7 V8 V9 V10 Vstack 0 1750 1770 1790 1810 1830 1850 1870 1890 1910 1930 1950 Time (hour) 35 Fuel Quality Workshop
Stacktest: GFC (First & Second 100 hours) EIS Cell voltage in time (10 A) GFC1 & GFC2 EIS 30 H2/N2 GFC1 H2/N2 GFC2 H2/N2 25 V1 V2 20 V3 V4 V (V) 15 10 5 V5 V6 V7 V8 V9 V10 Vstack 0 1600 1700 1800 1900 2000 2100 2200 2300 2400 Time (hour) 36 Fuel Quality Workshop
Stacktest: EIS before and after GFC gas 20 dc = 10 A; ac = 0.5 A, f = 100 khz - 0.01Hz, T=800-850 C, fuel: 40%H 2 /N 2 15 10 hours 1679 -Z" (ohm.cm²) 5 0-5 0 10 20 30 40 50 60 70 2328-10 -15-20 Z' (ohm.cm²) Only increase of the ohmic resistance, no poisoning of the anode 37 Fuel Quality Workshop
Conclusions The electrical efficiency of an SOFC operated with bio-syngas can be over 50% (LHV) C 2 H 2 /C 2 H 4 and C 7 H 8 are converted by SOFCs (> 99.2%) Higher hydrocarbons ( C 10 ) inhibit the catalytic CH 4 reforming reaction Influence of higher hydrocarbons ( C 10 ) on the electrochemical performance is low High temperature gas cleaning seems to be a suitable process for conditioning bio-syngas for SOFC 38 Fuel Quality Workshop