the effect of various biogas contaminants on sofc performance

Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy THE EFFECT OF VARIOUS BIOGAS
CONTAMINANTS ON SOFC
PERFORMANCE
Sulfur, chlorine and siloxane compounds. A. Lanzini*, G.A. Ortigoza-Villalba*, D. Papurello*, M. Santarelli*, R. Singh**, P. Leone*
*Department of Energy, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, (Italy)
**TOPSOE FUEL CELL A/S, Nymøllevej 66, DK-2800 Kgs. Lyngby (Denmark)
Effect of various biogas contaminants on SOFC performance – Papurello D. Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Outline 1.  SOFCOM project aim and scope 2.  Biogas plant – SMAT waste water treatment plant (WWTP) 3.  Impact of pollutants on short-‐stacks 4.  Sulfur compounds impacts and tolerable limits 5.  Chlorine compounds impacts and tolerable limits 6.  Siloxane compounds impacts and tolerable limits Effect of various biogas contaminants on SOFC performance – Papurello D. Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy SOFCOM aim and scope SOFCOM is an applied research project devoted to demonstrate the technical feasibility, the efficiency and environmental advantages of CCHP plants based on SOFC fed by different typologies of biogenous primary fuels (locally produced) also integrated by a process for the CO2 separation from the anode exhaust gases. Air
blower
Reformer
Oxycombustor
Air preheater
SOFC
Cooling
Air
CHP
Effect of various biogas contaminants on SOFC performance – Papurello D. Cleaning
system
CO2
separation
Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Biogas plant – SMAT waste water treatment plant (wwtp) Greatest waste water treatment plant in Italy, serving 2.2 millions equivalent inhabitants in Turin metropolitan area (26000 m3/h). Waste water treatment area: 4 parallel lines: biological “tertiary” treatment with nitrogen and phosphorus removal Sludge treatment line: > 6 digesters each 12000 m3, 17-‐20 day mean pre-‐dewatering, anaerobic digestion, post-‐
dewatering, drying. Treats over 6000 m3/day residence time; of sludge (2%tss) > 33000 Nm3/day biogas (2010) In absence of oxygen anaerobic microorganisms turn organic substances of sludge into biogas, a mix of methane (60-‐65%) and carbon dioxide (35-‐40%). Effect of various biogas contaminants on SOFC performance – Papurello D. Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy On-‐site measured contaminant concentrations in biogas (SMAT plant) Effect of various biogas contaminants on SOFC performance – Papurello D. Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Sulfur compounds detection On an H2S-‐equivalent basis, <70 ppm(v) on average in the biogas stream (in-‐situ abatement with iron-‐salts within the digester) Effect of various biogas contaminants on SOFC performance – Papurello D. Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Chlorine compounds detection Both inorganic and organic halogenated compounds present in the sewage biogas: HCl
HF
HBr
C2Cl4
C2H2Cl2
1
Concentration mg/nm3
0,9
0.5 ppmv HCl 0,8
0,7
0,6
0,5
50 ppbv C2Cl4 0,4
0,3
0,2
0,1
0
M1
M2
M3
Effect of various biogas contaminants on SOFC performance – Papurello D. M4
M5
M6
M7
Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Siloxane compounds detection C6H18O3Si3 (D3) Hexamethylcyclotrisiloxane C8H24O4Si4 (D4) Octamethylcyclotetrasiloxane Siloxanes are expected to be the most C10H30O5Si5 (D5) Decamethylcyclopentasiloxane dangerous compounds, regardless of the prime C8H24O2Si3 (L3) Octamethyltrisiloxane power downstream (engine, turbine or HTFC) Concentration mg/Nm3
D3
D4
D5
L2
L3
C6H18OSi2 (L2) Hexamethyldisiloxane C10H30O3Si4 (L4) Decamethyltetrasiloxane C12H36O4Si5 (L5) Dodecamethylpentasiloxane C3H10OSi L4
(TMS) Trimethylsilanol L5
TMS
20
15
1 ppmv D5 10
5
0
M1
M2
M3
Effect of various biogas contaminants on SOFC performance – Papurello D. M4
M5
M6
M7
Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Selected biogas contaminants for testing – experimental set up Ni-‐based anode supported fuel cells Short stack 200 W
Single cell
Type Sulfurous Contaminants range in AD biogas (ppmv) H2S 50-‐100 (average ~70) D4 < 1 Siloxanes D5 ~1 (max. 1.14) HCl ~1 Halogenated C2Cl4 < 1 Hydrocarbons C2Hon 4S, OFC C7pHerformance low 8 Effect of various biogas contaminants – Papurello D. Stack 20-250 kW
Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Stack operating conditions • 
• 
• 
• 
• 
Nominal power 200 We 20 A (0.2 A/cm2) ~700 °C (average T measured on air flow rate at inlet/outlet of the stack manifold plate) FU 60% biogas reformate (mol%): H2/CO/H2O/CO2 = 50/20/10/20 – (derived from biogas steam-‐
reforming with S/C = 2) Test ID Description Baseline threshold level tolerance to H2S Max. contaminant concentration Test Status Stack # Post-‐test 3 ppmv COMPLETED by TOFC 0 n.a. No carbon observed. Report included in D2.3. S traces observed. Report included in D2.3. 1a threshold level tolerance to C2H4 1,000 ppmv COMPLETED by POLITO 1 1b threshold level tolerance to COS 200 ppbv COMPLETED by POLITO 1 2a threshold level tolerance to C2Cl4 1 ppmv COMPLETED by POLITO 2 No Cl effects observed. 3 -‐ x threshold level tolerance to HCl 5 ppmv Failed due to compressor failure / water injection in the cathode side 2b threshold level tolerance to HCl 5 ppmv COMPLETED by POLITO 4 No Cl effects observed. 3 threshold level tolerance to D4 1 ppmv COMPLETED by POLITO 5 Effect of various biogas contaminants on SOFC performance – Papurello D. Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Sulfur compounds impacts and tolerable limits Sulfur added (3 ppmv) at the main biogas stream adsorbed on the Ni in the anode reaching an equilibrium coverage of the Ni. The cell voltage drops and stabilises, due to two effects: •  An increase in ASR due to sulfurs inhibition of electrochemistry; •  A drop in – Nernst potential due to the lower H2 and higher H2O concentrations in the stack Reversible performance tested with H2S concentration below 2 ppmv
Effect of various biogas contaminants on SOFC performance – Papurello D. Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Sulfur coverage H2S dissociative chemisorption on Ni-‐SOFC anode is best described by a Temkin-‐
like isotherm [Hansen*, 2008] The performance drop is linearly dependent with sulfur-‐coverage (ƟS) à Ni active sites (TPB) are progressively blocked 𝑝(𝐻↓2 𝑆)/𝑝(𝐻↓2 ) =exp(∆𝐻↑0 ×1−𝛼𝜃↓𝑠 /𝑅𝑇 −∆
Temkin-‐like isotherm 𝑆↑0 /𝑅 ) 𝜃↓𝑠 =1.45−9.53×10↑−5 𝑇+4.17×10↑−5 𝑇𝑙𝑛[𝑝(𝐻↓2 𝑆)/𝑝(𝐻↓2 ) ] 6,0%
Performance drop (%)
12,0%
Performance drop (%)
Sulfur-‐coverage = f(T,pH2S) y = 0,3357x - 0,1905
R² = 0,99714
10,0%
8,0%
6,0%
4,0%
2,0%
0,0%
0%
20%
40%
60%
80%
Sulfur coverage (ƟS)
100%
TOFC stack, 0 < H2S < 25 ppm(v), FU 60%,
2
T
= o700
°C,
i=
140 mA/cm
Effect f various biogas contaminants on SOFC performance – Papurello D. y = 0,477x - 0,3696
R² = 0,99081
5,0%
4,0%
3,0%
2,0%
1,0%
0,0%
60%
65%
70%
75%
80%
85%
90%
Sulfur coverage (Ɵs)
ASC commercial cell, 0 < H2S < 7 ppm(v), FU
30%, T = 750 °C, i = 300 mA/cm2
Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Chlorine compounds impacts and tolerable limits TOFC stack, 0 < HCl < 5 ppm(v) FU = 60%, T = 700 °C HCl up to 5 ppm(v) : no stack degradation (> 500 hr) Preliminary post-‐test analysis shows no evidence of Cl on Ni anode Effect of various biogas contaminants on SOFC performance – Papurello D. Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Pollutant coverage comparison Performance drop (%)
6,0%
5,0%
H2S
4,0%
HCl
3,0%
2,0%
j = 0.3 A/cm2 FU = 30% T = 750 °C H2S = 0.84 – 6.4 ppm(v) 1,0%
0,0%
1
10
100
Gas concentration (ppmv)
1000
A marked irreversible performance drop is observed with HCl only when > ~20 ppmv. At low p(Cl) in the anode stream, the performance loss is almost negligible. Effect of various biogas contaminants on SOFC performance – Papurello D. Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Effect of C2Cl4 (stack) C2Cl4 up to 1 ppm(v): no stack degradation (> 400 hr). Preliminary post-‐test analysis shows no evidence of Cl on Ni anode. C2Cl4 is converted to HCl on the SOFC anode according to equilibrium calculations. Effect of various biogas contaminants on SOFC performance – Papurello D. Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Results. Impact of D4 (siloxane, stack) 11-‐cells TOFC stack 0.07 < D4 < 1 ppm(v) FU = 60% T = 700 °C I = 20 A H2/CO/H2O/CO2 = 50/20/20/10) Effect of various biogas contaminants on SOFC performance – Papurello D. Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Results. Impact of D4 (siloxane, stack) Degradation rate (% per 1,000 hr)
30
25
20
R² = 0,98934
15
10
5
0
0
100
200
300
D4, ppb(v)
400
500
600
Already at 69 ppb(v) D4 affect strongly and irrevesibly the fuel cell performance Effect of various biogas contaminants on SOFC performance – Papurello D. Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy Conclusions – Effect of a single contaminant •  Light hydrocarbons are easily converted within the SOFC. Up to 1000 ppmv of C2H4 were fed to the SOFC without any problem. •  Siloxanes confirmed to be the most dangerous compounds for the SOFC, causing irreversible degradation even at sub-‐ppm level. This was confirmed both in single cell and stack experiments . •  H2S has a strong initial deactivation effect, which was well correlated with a Temkin-‐like isotherm. Reversible performance up to 2 ppmv. •  HCl and chlorine compounds are well tolerated by the Ni-‐SOFC up to few ppms (20 ppmv). Effect of various biogas contaminants on SOFC performance – Papurello D. Fifth European Fuel Cell Technology & Applications Conference -‐ Piero Lunghi Conference – December 11-‐13, 2013, Rome, Italy SOFCOM: SOFC CCHP WITH POLY-FUEL: OPERATION AND MAINTENANCE
Project coordinator: Prof. Massimo Santarelli (Politecnico di Torino, IT)
Duration: 3 years (Nov. 2011 – Oct. 2014).
www.sofcom.eu
Effect of various biogas contaminants on SOFC performance – Papurello D.

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