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Research Papers

The Efficiencies of Internal Reforming Molten Carbonate Fuel Cell Fueled by Natural Gas and Synthetic Natural Gas From Coal

[+] Author and Article Information
Hai-Kyung Seo

Mem. ASME
Clean Power Generation Laboratory,
KEPCO Research Institute,
105, Munji-Ro, Yuseong-Gu,
Daejeon 34056, South Korea
e-mail: seohk@kepco.co.kr

Won-shik Park

Mem. ASME
Clean Power Generation Laboratory,
KEPCO Research Institute,
105, Munji-Ro, Yuseong-Gu,
Daejeon 34056, South Korea
e-mail: wspark@kepco.co.kr

Hee Chun Lim

Mem. ASME
Clean Power Generation Laboratory,
KEPCO Research Institute,
105, Munji-Ro, Yuseong-Gu,
Daejeon 34056, South Korea
e-mail: hclim123@nate.com

1Corresponding author.

Manuscript received January 3, 2016; final manuscript received March 25, 2016; published online April 26, 2016. Assoc. Editor: Kevin Huang.

J. Electrochem. En. Conv. Stor. 13(1), 011005 (Apr 26, 2016) (10 pages) Paper No: JEECS-16-1002; doi: 10.1115/1.4033255 History: Received January 03, 2016; Revised March 25, 2016

When synthetic natural gas (SNG) is produced from coal and used as a fuel in the internal reforming molten carbonate fuel cell (ir-MCFC), electric efficiency can be no greater than 31%. This is because there are several exothermic reactions in the processes of converting coal to SNG, so that a maximum 64% of coal's energy is converted into SNG energy. This results in a lower efficiency than when the ir-MCFC with the electric efficiency of 48% is fueled by natural gas (NG). To increase electric efficiency with SNG, it is necessary to recover the exothermic heat generated from the processes of converting coal to SNG as steam, which can then be used in a steam turbine. When steam produced in the gasification, water gas shift (WGS), and methanation processes is used in a steam turbine, the gross electric efficiency will become 41%. If the steam and auxiliary power for CO2 capture process is consumed more, the net efficiency will be 27%. Use of additional steam from the exhausted gas of fuel cell can increase the total net efficiency to 49%.

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Figures

Grahic Jump Location
Fig. 1

Flow diagram of a 30 MW class ir-MCFC system fueled by NG. (Pipe 11, 23, 13, 4, 21, 22: NG to anode inlet, Pipe 5: anode outlet to combustor, Pipe 16, 19: combustor to cathode inlet, Pipe 6, 7, 8, 9: cathode exhaust gas, Pipe 1, 2, 3: air to combustor.) Apparatus 1: the stack of ir-MCFC, 2: heat exchanger for air heating, 3: heat exchanger for heating water, 4: heat exchanger for heating NG, 6: water, 7: NG, 8: air blower, 9: catalytic combustor, 10: Flare stack, 11: mixer of NG and steam, 12: heat exchanger for producing the superheated steam, 13: the valve splitting the steam, 14: air, 16: heat exchanger for cooling the catalytic combustor off-gas, 17: the additionally produced steam, 18: mixer of NG and CO2, and 19: CO2.

Grahic Jump Location
Fig. 2

Process of coal to SNG without heat recovery. Apparatus 1: gasifier, 2: coal, 3: syngas cooler, 4: ash remover, 5 and 6: the water and steam passing the water wall in the gasifier, 7: cooler, 8: the mixer, 9: the steam introduced into the WGS, 10: WGS reactor, 11: ash disposal, 12: cooler, 13 and 14: the inlet and outlet of steam recovering the heat from the syngas cooler, 15: 16; the inlet and outlet of steam recovering the heat, 17 and 18: S, CO2 capture and its disposal, 19: methanation first reactor, 20: 95% purified oxygen, 22: mixer, 23: cooler, 24: compressor, 25: cooler, 26: the valve splitting the first methanation gas, 27: the second methanation reactor, 32: cooler, 28, 29, 30, 31, 34, 35, 36, and 37: the steam recovering the heat, and 33: the produced SNG.

Grahic Jump Location
Fig. 3

Process of converting coal to SNG including the heat recovery in WGS and methanation (circles mean heat recovery parts). Apparatus 1–20, 22–27, 32, and 33: the same as in Fig. 2, apparatus 21: the steam drum, 38: the steam turbine, 40: the deaerator, 39: the condenser, 29, 30, and 41: the pumps, 42: water source.

Grahic Jump Location
Fig. 4

Process of converting coal to SNG including the heat recovery in gasification, WGS, and methanation (circles mean heat recovery parts). All apparatus are the same as in Fig. 3.

Grahic Jump Location
Fig. 5

Flow diagram of a 30 MW class ir-MCFC system fueled by SNG. (Pipe 9, 11, 4, 21, 22: SNG to anode inlet, Pipe 5: anode outlet to combustor, Pipe 16, 19: combustor to cathode inlet, Pipe 6, 7, 8: cathode exhaust gas, Pipe 1, 2, 3: air to combustor.) Most of all apparatuses are the same as in Fig. 1, except apparatus 7: SNG, and apparatus 4: the pressure reducer like the expander.

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