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

Content

INTRO

OBJECTIVES

METHODOLOGY

RESULTS

CONCLUSIONS

FUTURE WORKS

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

Intro

03

Mixed reforming of natural gas/biogas

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

10

Full algorithm

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

13

Steam reforming of methane, S/C=3

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).

Acknowledgement

19

Prof. Alex Goguet

Prof. David Rooney

Dr. Beatrice Smyth

Dr. Geoffrey McCullough

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

Results

20

Experimental results: catalysts screening

TFR:100 sccm, 60% CH4, 40% CO2, GHSV:50,000 mL gcat-1 h-1