Influence of Bio-Syngas Contaminants on SOFC

Transcription

1 Influence of Bio-Syngas Contaminants on SOFC BioCellus & Green Fuel Cell Bert Rietveld, Nico Dekker, Jan Pieter Ouweltjes

2 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: V; T: 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

3 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 C C 3 Fuel Quality Workshop

4 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

5 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

6 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

7 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

8 In case of complete conversion: CH 4 + H 2 O CO + 3 H 2 C 2 H H 2 O 2 CO + 3 H 2 C 2 H H 2 O 2 CO + 4 H 2 C 7 H H 2 O 7 CO + 11 H 2 C 10 H H 2 O 10 CO + 14 H 2 C 14 H H 2 O 14 CO + 19 H 2 C 16 H 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

9 In case of insufficient conversion: Graphitic carbon Encapsulating carbon Filamentous carbon Whisker-like carbon Pyrolytic carbon 9 Fuel Quality Workshop

10 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

11 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

12 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

13 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 Fuel Quality Workshop

14 Test rig: humidifiers (naphthalene) 14 Fuel Quality Workshop

15 Electrical efficiency (ESC) with clean bio-syngas ESC (850 C) 100% 90% Cell voltage (V) Cell voltage Fuel utilisation Efficiency 80% 70% 60% 50% 40% 30% 20% Fuel utilisation (%); Efficiency (%) % 0.0 0% Current density (A/cm²) Fuel utilisation = Fuel converted / Input Fuel Efficiency = Electricity Produced / Energy Input (LHV) 15 Fuel Quality Workshop

16 Impact of C 2 H y and C 7 H 8 on the ESC cell voltage 900 ESC CKS5E (850 C, 0.16 A/cm², U f =60%) ET C 2 H 2 /C 2 H 4 C 7 H 8 0.1% C 2 H % C 2 H % C 7 H 8 V (mv) Time (hours) Acetylene, ethylene and toluene act as fuel 16 Fuel Quality Workshop

17 Impact of C 14 H 10 and C 16 H 10 on the ESC cell voltage ESC CKS5E (850 C, 0.16 A/cm², U f =60%) C 14 H ppm C 16 H ppm ET V (mv) Time (hours) Deactivation by phenanthrene and pyrene 17 Fuel Quality Workshop

18 Impact of C 10 H 8 on the ESC cell voltage 900 ESC CKS5E (850 C, 0.16 A/cm², U f =60%) ET C 10 H ppm 800 V (mv) Time (hours) Deactivation by naphthalene 18 Fuel Quality Workshop

19 Impact of naphthalene on methane conversion ESC (850 C, 0.16 A/cm²,Uf =60%) C 10 H ppm GC data ET Outlet concentration (dry, %) H 2 CO 2.0 CH Time (hours) Higher tars inhibit the methane reforming 19 Fuel Quality Workshop

20 Effect of C 10 H 8 on the cell performance: H 2 as fuel 900 ESC (850 C, 0.14 A/cm²,Uf =53%) CKS5E ET Reference gas: H H 2 C 10 H ppm 800 V (mv) 750 I (A/cm 2 ) Time (hours) Slight effect of heavy tars on the electrochemical conversion of H 2 20 Fuel Quality Workshop

21 Single cell test-rig for real bio-syngas Heated duct for hot syngas 21 Fuel Quality Workshop

22 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

23 Bio-syngas composition at test locations 23 Fuel Quality Workshop

24 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

25 Results testing day 2 at TUDelft, low U f Tars > 10 g.m -3 No deactivation due to tars 25 Fuel Quality Workshop

26 Post test analysis TU Delft cell No traces of carbon species 26 Fuel Quality Workshop

27 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

28 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

29 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

30 Gasifier and Hot Temperature gas cleaning Ceramic filter - removal of particles HGF - filter 30 Fuel Quality Workshop

31 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

32 Gasifier and Hot Temperature gas cleaning Catalytic reactors for hydrogenation and reforming of unsaturated and aromatic hydrocarbons Catalytic reactors 32 Fuel Quality Workshop

33 Stack test Staxera stack (MK-100) - 30 cells - Active area: 81 cm²/cell - ESC - Temperature: C - Nominal output (H 2 /N 2 ): - 25 Volt at 10A (U f = 53%) 33 Fuel Quality Workshop

34 Stacktest: GFC (gasification) & SN (pyrolysis) SN1, GFC1, GFC2: Beechwood; SN2: Rofire; SN3: waste of carpet industry SN1 SN2 GFC1 GFC2 SN3 Vcell (V), Current (A) I Vstack Time (hour) Total operating time 5500 hours, degradation of 1%/1000 hours 34 Fuel Quality Workshop

35 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) V2 V3 V4 V5 V6 V7 V8 V9 V10 Vstack Time (hour) 35 Fuel Quality Workshop

36 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) V5 V6 V7 V8 V9 V10 Vstack Time (hour) 36 Fuel Quality Workshop

37 Stacktest: EIS before and after GFC gas 20 dc = 10 A; ac = 0.5 A, f = 100 khz Hz, T= C, fuel: 40%H 2 /N hours Z" (ohm.cm²) Z' (ohm.cm²) Only increase of the ohmic resistance, no poisoning of the anode 37 Fuel Quality Workshop

38 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