Performance Analysis of a MCFC/MGT Hybrid Power System Bi-Fueled by City Gas and Biogas
Abstract
:1. Introduction
2. Numerical Modeling and Experimental System
2.1. Molten Carbonate Fuel Cell Model
- (1)
- The cells in the module are similar to each other;
- (2)
- The boundaries for each cell are adiabatic;
- (3)
- The anode, cathode, and electrolyte layers are considered as one layer during thermal analysis.
Items | Value | Unit |
---|---|---|
9.84 × 10−3 | ohm·cm2 | |
23.80 | kJ·mol−1 | |
9.50 × 10−7 | ohm·cm2·atm0.5·K−1 | |
27.90 | kJ·mol−1 | |
6.91 × 10−15 | ohm·cm2·atm0.5·K−1 | |
179.20 | kJ·mol−1 | |
3.75 × 10−9 | ohm·cm2·K−1 | |
67.10 | kJ·mol−1 | |
1.07 × 10−6 | ohm·cm2 | |
95.20 | kJ·mol−1 |
Species | a | b | c |
---|---|---|---|
CH4 | −8.73653 | 0.025966 | 2.20 × 10−5 |
C2H6 | −9.12764 | 0.016874 | 6.06 × 10−5 |
C3H8 | −12.5028 | 0.0209687 | 9.08 × 10−5 |
C4H10 | −17.1319 | 0.0308405 | 1.17 × 10−4 |
H2 | −7.65941 | 0.0276503 | 1.43 × 10−6 |
CO | −7.68459 | 0.0273887 | 2.73 × 10−6 |
H2O | −8.77673 | 0.0309842 | 4.20 × 10−6 |
CO2 | −10.7092 | 0.0370774 | 7.79 × 10−6 |
O2 | −8.00066 | 0.0284986 | 2.90 × 10−6 |
N2 | −7.6341 | 0.0272345 | 2.61 × 10−6 |
2.2. Steam Reformer Model
2.3. Catalytic Combustor Model
2.4. Experimental System
MCFC Stack | 2 Stacks |
---|---|
Operation pressure (MPa) | 0.335 |
Cell Voltage (V) | 0.726 |
Current Density (mA·cm2) | 158 |
Stack temperature (°C) | 580/670 |
MCFC power (kW) | 300 |
MGT power (kW) | 50 |
3. Results and Discussion
3.1. Model Verification
City Gas (13A) | Biogas | ||||
---|---|---|---|---|---|
Species | Fraction | Heat Value | Species | Fraction | Heat Value |
(%) | (kJ·mol−1) | (%) | (kJ·mol−1) | ||
CH4 | 88.0 | 802.3 | CH4 | 0.5 | 802.3 |
C2H6 | 6.0 | 1428 | N2 | 48.2 | - |
C3H8 | 4.0 | 2043 | CO2 | 17.8 | - |
C4H10 | 2.0 | 2658 | CO | 21.6 | 283.0 |
- | - | - | H2 | 11.9 | 241.8 |
Sum | 100.0 | 926.8 | - | 100.0 | 93.9 |
Biogas Flow | Items | Power | Cathode Temperature | ||
---|---|---|---|---|---|
MCFC | MGT | Inlet | Outlet | ||
Nm3·h−1 | kW | kW | °C | °C | |
10 | Experiment | 148.4 | 21.66 | 579.9 | 629 |
Calculation | 146.3 | 21.6 | 578 | 626 | |
Difference (%) | 1.5 | 0.4 | 0.3 | 0.48 | |
20 | Experiment | 148.3 | 21.5 | 580.1 | 638.6 |
Calculation | 147.5 | 21.8 | 578.1 | 628.1 | |
Difference (%) | 0.5 | 1.3 | 3.5 | 1.6 |
3.2. Effect of City Gas and Biogas Bi-Fuel
3.3. System Response Analysis
4. Conclusions
- (1)
- The MCFC, steam reformer, and catalytic combustor models are in good agreement with the experimental results fueled by city gas only or bi-fueled by city gas and biogas.
- (2)
- The MFCF/MGT hybrid power system can be operated stably with added biogas flow rate up to 150.0 Nm3·h−1, which is about 50% of the overall input heat value with high overall power generation efficiency ranging from 39.0% to 42.0%.
- (3)
- The MCFC/MGT hybrid power system can be operated stably both at low amplitude with slow current change speeds and large amplitude with rapid power demand conditions.
- (4)
- The MCFC/MGT hybrid system bi-fueled by city gas and biogas is applicable in providing energy for the micro–grid network with wide amplitude.
Author Contributions
Conflicts of Interest
Nomenclature
A | heat transfer area (m2) |
Aa | the frequency factor of anode (ohm·cm2·atm0.5·k−1) |
Ac | the frequency factor of cathode (ohm·cm2·atm0.5·k−1) |
Air | the frequency factor of internal resistance on electrolyte (ohm·cm2) |
catw | catalyst weight (kg) |
the mole flow of electrons (kmol·h−1) | |
E | Nernst voltage (V) |
E0 | standard electrode potential (V) |
F | Faraday constant (s·A·mol−1) |
Finlet | inlet flow rate of gas (kmol·h−1) |
Foutlet | outlet flow rate of gas (kmol·h−1) |
h | heat transfer coefficient (W·m−2·K−1) |
ΔHa | activation energy of anode |
ΔHc | activation energy of cathode |
ΔHir | activation energy of internal resistance of the electrolyte (kJ·mol−1) |
i | current value (A) |
j | current density (A·m2) |
k | reaction rate constant |
Nu | Nusselt number |
P | pressure (atm) |
Pr | Prandtl number |
Q | reaction heat (J) |
Ra | anode resistance (ohm·cm2) |
Rc | cathode resistance (ohm·cm2) |
Rir | internal resistance on the electrolyte (ohm·cm2) |
Re | Reynolds number |
r | reaction rate (kmol·h−1) |
T | temperature (K) |
Uf | fuel efficiency (-) |
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Huang, H.; Li, J.; He, Z.; Zeng, T.; Kobayashi, N.; Kubota, M. Performance Analysis of a MCFC/MGT Hybrid Power System Bi-Fueled by City Gas and Biogas. Energies 2015, 8, 5661-5677. https://doi.org/10.3390/en8065661
Huang H, Li J, He Z, Zeng T, Kobayashi N, Kubota M. Performance Analysis of a MCFC/MGT Hybrid Power System Bi-Fueled by City Gas and Biogas. Energies. 2015; 8(6):5661-5677. https://doi.org/10.3390/en8065661
Chicago/Turabian StyleHuang, Hongyu, Jun Li, Zhaohong He, Tao Zeng, Noriyuki Kobayashi, and Mitsuhiro Kubota. 2015. "Performance Analysis of a MCFC/MGT Hybrid Power System Bi-Fueled by City Gas and Biogas" Energies 8, no. 6: 5661-5677. https://doi.org/10.3390/en8065661