Lignite as a fuel for direct carbon solid oxide fuel cell

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1 Lignite as a fuel for direct carbon solid oxide fuel cell Janusz Jewulski, Marek Skrzypkiewicz, Michał Struzik, Iwona Lubarska-Radziejewska Institute of Power Engineering Fuel Cell Department Augustowka 36, PL , Warsaw, Poland cop@ien.com.pl 1 Institute of Power Engineering

2 About the Institute of Power Engineering Institute of Power Engineering Founded in 1953 Located in 6 main cities across Poland Thermal, Electric and Mechanical Divisions Fuel Cell Department (Thermal Division) Field of research: SOFC cells and stacks Oxygen Permeation Membranes Direct Carbon SOFC Catalysis μchp system development 2 Institute of Power Engineering

3 Why lignite? Poland: 34% of electricity generated by conventional lignite powered power plants. Other European countries the situation is similar: Greece 59,6%, Czech Rep. 51,3%, Germany 23,5%, Turkey 33%. A high efficiency fuel cell powered by lignite could be an alternative for steam turbines in many countries. There are large reserves of lignite across the world (150 bln tons -> ca. 170 years). J. Soliński, Energetyka, Institute of Power Engineering

4 Selected types of Direct Carbon Fuel Cell O 2- DC-SOFC Anode: C + 2 O 2- CO e - Cathode: O e - 2 O 2- Summary: C + O 2 CO 2 Carbon Węgiel Anode Anoda Electrolyte Elektrolit Katoda Cathode Cathode Katoda Oxidant Oxidant + CO 2 Oxidant CO 3 2- DC-MCFC Anode: C + 2 CO CO e - Carbon Węgiel Anode Anoda Electrolyte Elektrolit Cathode: O CO e - 2 CO 2-3 Summary: C + 2 (CO 2 ) kat. + O 2 3 (CO 2 ) an. OH - DC-AFC Anode: C + 4 OH - 3CO e - Carbon Węgiel Anode Anoda Electrolyte Elektrolit Cathode Katoda Cathode: O H 2 O + 4 e - 4 OH - Summary: C + O (H 2 O) kat. CO (H 2 O) an. Sn, SnO x Carbon Węgiel + stopiona sól Anode + Liquid Anoda Tin Carbon Węgiel + + stopiona sól Carbonate Anode Anoda O 2- Oxidant Electrolyte Elektrolit Cathode Katoda O 2 - Oxidant Electrolyte Elektrolit Cathode Katoda DC-Molten Metal Anode SOFC Anode: Sn + 2 O 2- SnO e - C + SnO 2 CO 2 + Sn Cathode: O e - 2 O 2- Summary: C + O 2 CO 2 Hybrid: DC-Molten Carbonate SOFC Anode: C + 2 O 2- CO e - C + 2 CO CO e - CO 2 + O 2- CO 3 2- Cathode: O e - 2 O 2- Summary: C + O 2 CO 2 4 Institute of Power Engineering

Direct Carbon Solid Oxide Fuel Cell: reactions 4- electron electrochemical

+ O 2 CO 2 2- electron electrochemical reaction: Anode: C + O 2- CO + 2 e -

reaction : Anode: CO + O 2- CO 2 + 2 e - Cathode: ½ O 2 + 2 e - O 2- Summary:

5 Direct Carbon Solid Oxide Fuel Cell: reactions 4- electron electrochemical reaction: Anode: C + 2 O 2- CO e - Cathode: O e - 2 O 2- Summary: C + O 2 CO 2 2- electron electrochemical reaction: Anode: C + O 2- CO + 2 e - Cathode: ½ O e - O 2- Summary: C + ½ O 2 CO 2- electron electrochemical reaction : Anode: CO + O 2- CO e - Cathode: ½ O e - O 2- Summary: CO + ½ O 2 CO 2 Boudouard reaction (chemical): C + CO 2 2 CO 5 Institute of Power Engineering

C Electric power Considered paths of lignite processing for

6 Lignite conversion paths to electric power Gasification CO/CO 2 mixture Lignite Fuel processing Lignite char S O F C Electric power Considered paths of lignite processing for electricity generation in SOFC. 6 Institute of Power Engineering

7 Test stand Simplified scheme of the experimental setup. 7 Institute of Power Engineering

8 Cell assembly scheme Cell data and experimental conditions. Standard operating conditions Tested cells t = C p = 1 atm Fuel Cell Materials Nextcell 5 (ES-SOFC) 150μm(+/-15 μm) Hionic zirconia-based electrolyte 50 μm Ni-GDC/Ni-YSZ multi-layer anode 50 μm LSM/LSM-GDC multi-layer cathode Active area 16 cm 2 Simplified cell assembly scheme. Fuel Gas Chromatograph Electronic load Pulverized, Carbonaceous Varian CP-4900 Chroma 6310 series 8 Institute of Power Engineering

9 Tests with CO/CO 2 gas mixtures Polarization and power density curves for selected CO in CO 2 concentrations. Gas mixture humidified at: 25 C; operating temperature: 850 C. 9 Institute of Power Engineering

10 Tests with CO/CO 2 gas mixtures Polarization and power density curves for 50% CO in CO 2 at the selected temperatures. Grey line 850 C, 50% H 2 in N 2 humidified at room temperature (for comparison). 10 Institute of Power Engineering

11 Fuel preparation Raw Lignite Pre-grinding in mortar Drying SEM image of raw lignite Grinding in mortar Heat treatment (1123 K) SEM image of lignite char 11 Institute of Power Engineering

12 Lignite and lignite char parameters Parameter Unit Lignite Lignite char Water content % 6,9 1,7 Ash % 16,4 34,9 Volatile matter % 42,36 3,79 HHV kj/kg LHV kj/kg C % 50,7 62,0 H % 3,95 0,64 N % 0,53 0,69 S tot % 1,16 1,65 EDS maps showed few % of Ca and traces of Fe, known as catalysts of Boudouard reaction. 12 Institute of Power Engineering

Tests with lignite Lignite at 850 C: OCV = 1,117 V MPD = 93,3 mw/cm 2 ASR = 2,16 Ωcm 2 Maximum power density value close to activated carbon (96 mw/cm 2 ) Despite high impurities content in the fuel,

13 Tests with lignite Lignite at 850 C: OCV = 1,117 V MPD = 93,3 mw/cm 2 ASR = 2,16 Ωcm 2 Maximum power density value close to activated carbon (96 mw/cm 2 ) Despite high impurities content in the fuel, cell performance in the 2 nd run are comparable to observed in the 1 st run Polarization and power density curves for DC-SOFC fuelled with lignite. First and second run data are presented. 13 Institute of Power Engineering

14 Tests with lignite char Lignite char at 850 C: OCV = 1,11 V MPD = 143,8 mw/cm 2 ASR = 1,52 Ωcm 2 Strong temperature dependence on MPD OCV is growing with T (Boudouard reaction influence) Polarization and power density curves for DC-SOFC fuelled with 12g of Lignite char, selected temperatures presented 14 Institute of Power Engineering

More CO in exhaust gases is observed when cell is under load.

15 Test with lignite char GC measurement of the exhaust gas under OCV and DC load 62,5 ma/cm 2. More CO in exhaust gases is observed when cell is under load. Equilibrium concentrations for Boudouard reaction, p = 1atm. T. Reed, MIT Press (1971) 15 Institute of Power Engineering

16 Test with lignite char Temperature cycling (first 10h) Linear drop under constant current load (62,5 ma/cm 2 ) operation Fuel used up (steep drop in last 8h) Conversion of carbon from lignite char to electricity was calculated: Conv.= W el LHV in m in m out = 28,5% Remaining 71,5% is attributed to: - CO content in exhaust gas (CO/CO 2 ratio >>1) - Thermodynamics heat generation Batch operation of DC-SOFC fuelled with Lignite char 16 Institute of Power Engineering

17 Results summary Unit 50%CO Lignite Lignite char OCV V 0,909 1,117 1,11 MPD mw/cm 2 276,8 93,3 143,8 ASR Ωcm 2 0,70 2,16 1,52 17 Institute of Power Engineering

18 Conclusions Electrolyte supported SOFC can be fuelled with both gaseous and solid carbonaceous fuels. A fuel pre-processing path (thermal processing) was proposed and validated experimentally: Power density increased from 93,3 mw/cm 2 to 143,8 mw/cm 2 (54% higher) OCV with a change of -7 mv (0,62%) ASR decreased from 2,16 Ωcm 2 to 1,52 Ωcm 2 (30% lower) High Boudouard reaction rate is observed GC measurements and low conversion of carbon to electrical work. Lignite is a promising fuel for a DC-SOFC but degradation will be an issue. 18 Institute of Power Engineering

19 Thank you for your kind attention! Institute of Power Engineering Fuel Cell Department Augustowka 36, PL , Warsaw, Poland 19 Institute of Power Engineering

Carbon as a fuel for efficient electricity generation in carbon solid oxide fuel cells

Carbon as a fuel for efficient electricity generation in carbon solid oxide fuel cells Marek Skrzypkiewicz1,a and Magdalena Dudek2 1 Institute of Power Engineering, Thermal Processes Department, Ul. Augustówka