Reforming of biogas to hydrogen: a multi-criteria ...720916... · Reforming of biogas to hydrogen: a multi-criteria thermodynamic investigation Fabio De Rosa1, G. McCullough2, D.
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Reforming of biogas to hydrogen: a multi-criteria
thermodynamic investigation
Fabio De Rosa1, G. McCullough2, D. Rooney1, B. Smyth2, A. Goguet1
1 School of Chemistry and Chemical Engineering, CenTACat, Queen’s University Belfast2 School of Mechanical and Aerospace Engineering, Queen’s University Belfast
Linkoping, 7th September 2016
Intro
01
Diesel/Stirling enginePEM fuel cell
1-3kW electrical (residential applications) Combined heat and power generation; Carbon savings; Feed-in tariffs.
Decentralized hydrogen production
Intro
01
The use of hydrogen for energetic purposes could lead to sustainable and more secure energy supplies [1]
Decentralized hydrogen production
Diesel/Stirling enginePEM fuel cell
[1] F. Mueller-Langer, E. Tzimas, M. Kaltschmitt, S. Peteves, International Journal of Hydrogen Energy, 32 (2007) 3797-3810
Intro
01
Small-scale reforming technologies (less capital investment); Refuelling unit tailored to the refuelling site requirements; Reforming unit located at the refuelling site (no extensive H2 delivery infrastructure); No need for H2 storage (very light and flammable gas).
Decentralized hydrogen production
Diesel/Stirling enginePEM fuel cell
Intro
02
Decentralized hydrogen production
• The most economical way to obtain hydrogen as an energy vector is steam reforming of methane/natural gas;
• there is a great interest about auto-thermal reforming and dry reforming of methane/biogas (for practical applications H2O and/or O2 have to be added to the reaction mixture)
Intro
02
Decentralized hydrogen production
• Carbon accumulation on the catalyst surface;• C-H bond is very stable and difficult to be activated (800-1000°C);
High costs associated; Sintering of the catalyst; Exergy lost due to combustion in the heating stage [2]
[2] A.P. Simpson, A.E. Lutz, International Journal of Hydrogen Energy, 32 (2007) 4811-4820
Objectives
04
Issues:
Complex network of reactions;
Carbon deposition leading to catalyst replacement;
Up to two thirds of the overall cost of hydrogen production are for feed,
fuel and utilities [3].
Costs and carbon deposition can be lowered by selecting processes and
catalysts which allows low cost feedstock and by selecting optimum
process conditions giving low energy consumption
[3] W. Winter-Madsen, H. Olsson, Haldor Topsøe A/S, Denmark (online)
Problems statement
Objectives
05
To investigate the effect of operating conditions on the energy
requirements, carbon formation and the equilibrium composition of
hydrogen-rich gas produced via mixed reforming of biogas.
Parameter optimization: O2/CH4, H2O/CH4, CO2/CH4, Temperature
• Coke formation not always considered;
• One dimensional analysis (one criteria at a time);
• No Water-Gas Shift stage;
• Narrower ranges investigated;
• First-time application of the MCDM techniques as operating conditions optimization tool
Objectives
06
Mixed reforming of biogas: literature review
Methodology
Thermodynamic simulations
07
- THTS=325°C;
- TLTS=250°C;
- EquilibriumSRM:CH4, H2O, CO, H2, CO2, C(s)
- EquilibriumSHIFT:CO, H2, CO2, H2O
- Basis: 1 mol s-1 CH4
- TSRM=300-1200°C;
- P=1atm;
- EoS=Peng-Robinson;
- Air=79%N2, 21%O2;
- TH1=120°C;
Methodology – MCDM techniques
08
Technique for Order Preference by Similarity to the Ideal Solution
(TOPSIS)
• Alternatives are ranked according to the closeness to the Positive Ideal Solution (C*);
• At the PIS all the benefit criteria are maximized and the costs minimized;
• It needs information about the relative importance of the criteria (weights)
Methodology – MCDM techniques
09
Entropy method
• Used to determine the objective weights of the indexes for MCDM problems ;
• It measures the quantity of useful information provided by data itself (width of data
distribution);
Methodology – MCDM techniques
11
Criteria under exam
CH4 conversion:
H2 yield:
CO2 yield:
Thermal efficiency:
CO yield:
COKE yield:
Heat duty(SRM)
𝑥𝐶𝐻4 = 100𝐶𝐻4𝐼𝑁 − 𝐶𝐻4𝑂𝑈𝑇
𝐶𝐻4𝐼𝑁
𝑌𝐻2 = 1002 𝐻2𝑂𝑈𝑇 −𝐻2𝐼𝑁4𝐶𝐻4𝐼𝑁 + 2𝐻2𝑂𝐼𝑁
𝑌𝐶𝑂2 = 100𝐶𝑂2𝑂𝑈𝑇 − 𝐶𝑂2𝐼𝑁
𝐶𝐻4𝐼𝑁
𝜂𝐿𝐻𝑉 =𝐻2𝑂𝑈𝑇 ∗ 𝐿𝐻𝑉𝐻2𝐶𝐻4𝐼𝑁 ∗ 𝐿𝐻𝑉𝐶𝐻4
𝑌𝐶𝑂 = 100𝐶𝑂𝑂𝑈𝑇 − 𝐶𝑂𝐼𝑁
𝐶𝐻4𝐼𝑁
𝑌𝐶𝑂𝐾𝐸 = 100𝐶𝑂𝐾𝐸𝑂𝑈𝑇 − 𝐶𝑂𝐾𝐸𝐼𝑁
𝐶𝐻4𝐼𝑁
Results
12
Steam reforming of methane, S/C=3
Literature MCDM_1D
H2O/CH4=3 H2O/CH4=3
T(°C) 800 855
xCH4 99.773 99.933
YH2 19.818 19.849
YCO2 99.09 99.246
YCO 0.683 0.687
YCOKE 0 0
SRM(kW) 346.77 358.717
η_LHV 0.301 0.301
C* 0.995593 0.995645
Results
14
Literature MCDM_1D MCDM_2D
H2O/CH4=3 H2O/CH4=3 H2O/CH4=3.3
T(°C) 800 855 795
xCH4 99.773 99.933 99.798
YH2 19.818 19.849 18.73
YCO2 99.09 99.246 99.269
YCO 0.683 0.687 0.529
YCOKE 0 0 0
SRM(kW) 346.77 358.717 353.485
η_LHV 0.301 0.301 0.301
C* 0.995593 0.995645 0.995772
Steam reforming of methane, S/C=3
Results
15
Literature MCDM_1D MCDM_2D
H2O/CH4=3 H2O/CH4=3 H2O/CH4=3.3
T(°C) 800 855 795
xCH4 99.773 99.933 99.798
YH2 19.818 19.849 18.73
YCO2 99.09 99.246 99.269
YCO 0.683 0.687 0.529
YCOKE 0 0 0
SRM(kW) 346.77 358.717 353.485
η_LHV 0.301 0.301 0.301
C* 0.995593 0.995645 0.995772
Steam reforming of methane, S/C=3
Results
16
Mixed reforming of biogas
Topt(°C) O2/CH4opt H2O/CH4opt
CH4%=100 756.4 0.1 1.5CH4%=80 756.4 0.1 1.8CH4%=70 756.4 0.1 1.9CH4%=60 750.5 0.1 2.3
CH4%=50 774.1 0.2 2.9
CH4%=40 768.2 0.2 3.7
Conclusion
17
• Development of a comprehensive decision making technique able to assist during the
choice of the operating conditions for biogas reforming to hydrogen:
Multiple thermal processes;
Multiple criteria;
Objective and easy to implement
• Optimal operating conditions for biogas reforming:
T=750-770°C, O2/CH4=0.1-0.2, H2O/CH4=1.5-3.7
Future work
18
• Additional criteria (exergy analysis, economic criteria);
• Comparison of the optimal outcome for the biogas thermal processing with a novel
small-scale reforming technology (plasma processing).
Thanks for listening
This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement n. 316838
Project coordinated by the QUESTOR Centre at Queen’s University Belfast www.qub.ac.uk/questor
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