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TECHNICAL PAPERS: Microturbines & Small Turbomachinery

Comparative Performance Analysis of Internal and External Reforming of Methanol in SOFC-MGT Hybrid Power Plants

[+] Author and Article Information
Daniele Cocco

Department of Mechanical Engineering, University of Cagliari, Piazza D’armi, 09123 Cagliari, Italycocco@dimeca.unica.it

Vittorio Tola

Department of Mechanical Engineering, University of Cagliari, Piazza D’armi, 09123 Cagliari, Italy

J. Eng. Gas Turbines Power 129(2), 478-487 (Feb 01, 2006) (10 pages) doi:10.1115/1.2364009 History: Received October 01, 2005; Revised February 01, 2006

Abstract

SOFC-MGT hybrid power plants are a very attractive near term option, as they achieve efficiencies of over 60% even for small power outputs $(200–400kW)$. The SOFC hybrid systems currently developed are fuelled with natural gas, which is reformed inside the same stack at about $800–900°C$. However, the use of alternative fuels with a lower reforming temperature can lead to enhanced performance of the hybrid power plant. This paper reports a comparative performance analysis of SOFC-MGT power plants fuelled by methane and methanol. Since the reforming temperature of methanol $(250–300°C)$ is significantly lower than that of methane $(700–900°C)$, for the methanol fuelled plant both internal and external reforming have been examined. The performance analysis has been carried out by considering different values for the most important operating parameters of the fuel cell. The comparative analysis has demonstrated that simply replacing methane with methanol in SOFC-MGT power plants with internal reforming slightly reduces the efficiency. However, the use of methanol in SOFC-MGT power plants with external reforming enhances efficiency significantly (by about 4 percentage points). The use of methanol with external fuel reforming raises efficiency of the stack thanks to the improved heat management and to the higher hydrogen partial pressure at the anode inlet.

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Figures

Figure 17

Partial pressures ratio of H2 and H2O versus UF and SCR, using internal and external methanol reforming

Figure 18

Voltage of the SOFC stack versus UF and SCR, using internal and external methanol reforming

Figure 1

Conceptual scheme of the SOFC stack

Figure 5

Configuration of the SOFC-MGT power plant with external methanol reforming

Figure 6

Heat ratio QREF∕QAIR for the internally reformed SOFC stack fuelled with methane and methanol versus UF and SCR

Figure 7

Air utilization factor of the internally reformed SOFC stack fuelled with methane and methanol versus UF and SCR

Figure 8

Efficiencies of the internally reformed SOFC stack and the SOFC-MGT plant versus UF and SCR

Figure 9

Power outputs of the internally reformed SOFC stack and the SOFC-MGT plant versus UF and SCR

Figure 10

Ratio of the average partial pressures of H2 and H2O versus UF and SCR

Figure 11

Voltage of the internally reformed SOFC stack versus UF and SCR

Figure 2

Cell voltage and power density versus current density and cell operating pressure

Figure 3

Cell voltage and power density versus fuel utilization factor and cell operating temperature

Figure 4

Configuration of the SOFC-MGT power plant with internal reforming

Figure 12

Power ratio PSOFC∕PMGT for the internally reformed hybrid SOFC-MGT plant versus UF and SCR

Figure 13

SOFC air inlet temperature and flue gas exit temperature of the internally and externally reformed hybrid plant fuelled with methanol versus UF and SCR

Figure 14

Air utilization factor of the internally and externally reformed SOFC stack fuelled with methanol versus UF and SCR

Figure 15

Efficiencies of the SOFC stack and the SOFC-MGT plant versus UF and SCR, using internal and external methanol reforming

Figure 16

Power outputs of the SOFC stack and the SOFC-MGT plant versus UF and SCR, using internal and external methanol reforming

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