Thermodynamic analysis of fuel composition and effects of different dimethyl ether processing technologies on cell efficiency

doi:10.1016/j.fuproc.2020.106391

Fuel Processing Technology

Volume 203, 15 June 2020, 106391

https://doi.org/10.1016/j.fuproc.2020.106391 Get rights and content

Highlights

•
Carbon depositions are investigated for different DME processing technologies.
•
Fuel compositions are investigated for different DME processing technologies.
•
Effects of DME processing technologies on cell efficiency are investigated.
•
Suitable O/C ratio can improve cell efficiency and depress carbon deposition.

Abstract

Solid oxide fuel cell (SOFC) is one of the most attractive energy conversion systems, while dimethyl ether (DME) is an alternative clean fuel, and thus the application of DME in SOFC has great attraction. Fuel compositions are mainly determined by fuel processing technologies, which can affect the cell efficiency. In this paper, the relationships among fuel composition, oxygen to carbon (O/C) ratio, carbon deposition and cell efficiency are investigated for different DME processing technologies. According to the calculated results, SOFC with steam reforming of DME has the highest efficiency at the same O/C ratio and equivalent fuel utilization, while for catalytic partial oxidation of DME, the cell efficiency decreases rapidly with the increase of O/C ratio. The efficiency of SOFC with CO₂ reforming of DME decreases with the increase of O/C ratio, especially at high O/C ratio and low equivalent fuel utilization. When the O/C ratio is 1.5, solid carbon can't be formed, where the cell efficiencies are 51.7% for steam reforming of DME, 42.2% for DME reforming with H₂O and O₂, 32.7% for catalytic partial oxidation of DME, 49.3% for DME reforming with anode off-gas and 41.4% for CO₂ reforming of DME at 80% equivalent fuel utilization.

Graphical abstract

Introduction

The development of clean fuels and efficient energy conversion technologies is critical for a sustainable future [1]. Dimethyl ether is a so-called “clean fuel”, which has the advantages of high energy density, lower emission, no toxicity and ease of storage and transportation. It can be produced from a wide range of primary fuels including crude oil, residual oil, coal, syngas, biomass and waste products [[2], [3], [4]]. As a clean fuel, it is free from sulfur, heavy metals and other impurities [5]. Solid oxide fuel cell is one of the most attracting energy conversion systems because of high efficiency and excellent fuel flexibility, having the ability to use hydrocarbon as fuel for its high operating temperature [[6], [7], [8], [9]]. Application of DME in fuel cells is highly attractive because it combines the benefits of environmental friendliness of DME fuel and high efficiency of fuel cells. Recently, DME-fueled SOFC has attracted the attention of many researchers [[10], [11], [12], [13], [14]].

Dimethyl ether is being either directly supplied or reformed in a reformer before supplying to fuel cells. Direct electrochemical oxidation of DME on the anode is an ideal way, however, not being able to avoid severe carbon deposition [13,15], thus generally integrating solid oxide fuel cell with DME processing system. DME only has C single bond H and CO bond, no CC bond and contains about 35% oxygen, so it is easy to be converted to hydrogen and CO for SOFC. There are several technologies for pre-treating DME, for example, steam reforming of DME [[16], [17], [18]], catalytic partial oxidation of DME [1], carbon dioxide reforming of DME [19], autothermal reforming of DME [20] and DME reforming with anode off-gas as illustrated in Fig. 1. The fuel composition, hydrogen to carbon (H/C) ratio and O/C ratio can be greatly affected by the fuel processing technologies [21]. The H/C and O/C ratios in the fuel can affect the cell performance apparently [22,23]. Steam reforming of DME can easily produce the syngas with high H/C and O/C ratios, while for CO₂ reforming of DME, the H/C and O/C ratios can't reach too high.

CO₂ and H₂O are the oxidative products of electrochemical reactions, which can increase the concentration polarization, thus greatly affecting the cell performance. With the increase of fuel utilization, the cell performance decreases apparently for more CO₂ and H₂O produced, especially for anode-supported solid oxide fuel cell. On the other hand, the bad cell stability for redox behavior in special areas of the anode due to high fuel utilization [24], thus choosing the fuel utilization of ca. 65–95% [25,26].

Many researchers [[27], [28], [29]] have given the thermodynamic analysis of DME reforming, while not investigated the effects of DME processing technologies on the cell efficiency. Efficiency and long-term stability are important indicators for SOFC application, so it has an important significance for SOFC to investigate the relationships among carbon deposition, fuel composition and cell efficiency from different DME processing technologies.

In this paper, the fuel compositions and effects of different DME processing technologies on cell efficiency are investigated. The relationships among carbon deposition, O/C ratio, H/C ratio, fuel utilization and cell efficiency are also investigated for solid oxide fuel cell with the fuel from different DME processing technologies.

Section snippets

Calculation method

The program Gaseq (Version 0.79) is used to calculate the fuel compositions from different DME processing technologies, which employs the “therm.dat” databases from CHEMKIN, Burcat's compilation and the NASA database, and bases on the method of the minimisation of free energy (NASA method). According to the thermodynamic equilibrium results, there is little methanol in the products, and the products are mainly composed of H₂ (g), H₂O (g), CO (g), CO₂ (g), CH₄ (g) and solid carbon for different

Fuel compositions and cell efficiency from catalytic partial oxidation of DME

Catalytic partial oxidation of DME is an attractive alternative to produce syngas, which is an exothermic and highly selective process. It produces the syngas with hydrogen to carbon monoxide ratio of 3:2. Fig. 3 shows the fuel compositions from catalytic partial oxidation of DME at different O/C ratios and 1073 K. With the increase of O/C ratio, the ratio of solid carbon decreases gradually. When the O/C ratio increases to 1.1, solid carbon disappears completely, as illustrated in Fig. 3. When

Carbon deposition, O/C ratio and cell efficiency from different DME processing technologies

Carbon deposition is a serious problem in DME-fueled SOFC. Solid carbon is mainly determined by the O/C ratio in the fuel according to the thermodynamic equilibrium results. When the O/C ratio is lower than 1.1, solid carbon can be formed, while when the O/C ratio is larger than 1.1, solid carbon can't be formed at 1073 K. High O/C ratio in the fuel can depress the carbon deposition.

Fig. 13 shows the effects of O/C ratio on cell efficiencies from different DME processing technologies. The cell

Conclusions

The fuel composition, H/C ratio, O/C ratio and cell efficiency can be affected by the DME processing technology. When the O/C ratio is high, solid carbon can't be formed, but the cell efficiency may decrease. For steam reforming of DME, the cell efficiency is the highest at the same O/C ratio and equivalent fuel utilization. Catalytic partial oxidation of DME is an attractive process for it is an exothermic process, but the cell efficiency is lower. The cell efficiency from CO₂ reforming of DME

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The authors gratefully acknowledge the financial supports from the Ministry of Science and Technology of China (Grant No. 2016YFE0118300) and Chris Morley for Gaseq program.

References (36)

C. Su et al.
Reducing the operation temperature of a solid oxide fuel cell using a conventional nickel-based cermet anode on dimethyl ether fuel through internal partial oxidation
J. Power Sources
(2011)
Z. Azizi et al.
Dimethyl ether: a review of technologies and production challenges
Chem. Eng. Process.
(2014)
M.R. Rahimpour et al.
Assessment and comparison of different catalytic coupling exothermic and endothermic reactions: a review
Appl. Energy
(2012)
R. Peláez et al.
Catalyst deactivation in the direct synthesis of dimethyl ether from syngas over CuO/ZnO/Al₂O₃ and γ-Al₂O₃ mechanical mixtures
Fuel Process. Technol.
(2018)
E. Yasari
Improved dynamic performance of a thermally efficient reactor through water removal and defining new objective functions
Fuel Process. Technol.
(2019)
T. Huang et al.
Fuel processing in direct propane solid oxide fuel cell and carbon dioxide reforming of propane over Ni–YSZ
Fuel Process. Technol.
(2011)
M.C. Steil et al.
Durable direct ethanol anode-supported solid oxide fuel cell
Appl. Energy
(2017)
J. Zheng et al.
Steam reforming of liquid hydrocarbon fuels for micro-fuel cells. Pre-reforming of model jet fuels over supported metal catalysts
Fuel Process. Technol.
(2008)
C. Su et al.
Coke formation and performance of an intermediate-temperature solid oxide fuel cell operating on dimethyl ether fuel
J. Power Sources
(2011)
N. Laosiripojana et al.
Catalytic steam reforming of dimethyl ether (DME) over high surface area Ce–ZrO₂ at SOFC temperature: the possible use of DME in indirect internal reforming operation (IIR-SOFC)
Appl. Catal. A-Gen.
(2007)

Z. Ma et al.

CO₂ reforming of dimethyl ether over Ni/γ-Al2O3catalyst

Catal. Commun.

(2012)

S. Choi et al.

Autothermal reforming of dimethyl ether with CGO-based precious metal catalysts

J. Power Sources

(2016)

A. Machocki et al.

Hydrogen-rich gas generation from alcohols over cobalt-based catalysts for fuel cell feeding

Fuel Process. Technol.

(2016)

B. Tu et al.

IT-SOFC operated with catalytically processed methane fuels

Stud. Surf. Sci. Catal.

(2007)

D. Waldbillig et al.

Thermal analysis of the cyclic reduction and oxidation behaviour of SOFC anodes

J. Power Sources

(2005)

T.A. Semelsberger et al.

Thermodynamic equilibrium calculations of dimethyl ether steam reforming and dimethyl ether hydrolysis

J. Power Sources

(2005)

T.A. Semelsberger et al.

Thermodynamic equilibrium calculations of hydrogen production from the combined processes of dimethyl ether steam reforming and partial oxidation

J. Power Sources

(2006)

K. Faungnawakij et al.

Thermodynamic analysis of carbon formation boundary and reforming performance for steam reforming of dimethyl ether

J. Power Sources

(2007)

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Thermodynamic analysis of fuel composition and effects of different dimethyl ether processing technologies on cell efficiency

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Calculation method

Fuel compositions and cell efficiency from catalytic partial oxidation of DME

Carbon deposition, O/C ratio and cell efficiency from different DME processing technologies

Conclusions

Declaration of competing interest

Acknowledgments

J. Power Sources

Chem. Eng. Process.

Appl. Energy

Fuel Process. Technol.

Fuel Process. Technol.

Fuel Process. Technol.

Appl. Energy

Fuel Process. Technol.

J. Power Sources

Appl. Catal. A-Gen.

Catal. Commun.

J. Power Sources

Fuel Process. Technol.

Stud. Surf. Sci. Catal.

J. Power Sources

J. Power Sources

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