Introduction to deposit and high temperature corrosion probe
tests in 30 kW BFB during combustion of wood pellets doped
with ZnCl2 – first results
Dorota Bankiewicz(a), Elisa Alonso
Alonso--Herranz(b), Patrik Yrjas(a), Tor Laurén(a),
Hartmut Spliethoff(b), and Mikko Hupa(a)
a
b
Process Chemistry Centre, Åbo Akademi
Lehrstuhl für Energiesysteme, Technische Universität München
Finnish Swedish Flame Days, January 28-29, Naantali
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Background…sources
sources of Zn ?
Demolition wood, RWW
Municipal solid waste
surface treated wood (white pigment)
metal parts
metallic zinc in industrial paints
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Background…effect
effect
Biomass combustion and co-combustion and
waste incineration increase:
• fouling
• slagging
• corrosion of superheaters
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Background…advantages
advantages
Demolition wood, RWW
Municipal solid waste
Immediate volume and weight reduction
1 tone of waste = 3,5 MWth of energy
Energy generation - cost can be offset by
heat recovery/ energy sale
Ash residue is usually nonnon-putrescible
putrescible,,
sterile, inert
Small disposal area required
[1] Wood pellets-basic training (2007).
[2] Municipal Solid Waste Incineration. Learning Tool
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Outline of TUM 30kW BFB
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Outline of corrosion probe
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Samples treatment
•
Steel rings were cleaned in ethanol using the ultrasound bath
•
The material rings were fixed on the probe and introduced into the freeboard
•
After the corrosion test, the test rings were cooled down to room temperature
outside the furnace.
•
The rings were then placed in resin thinned with acetone.
•
After that the rings were fully cast in resin and cut off in the middle.
•
SEM/EDX analyses
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Tests matrix
Materials: 10CrMo, S28
Probe residence time: 28h, 7h
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Steel compositions
36,11
Sanicro 28
27,36
3,51
31,38
Fe
Cr
Mo
Mn
Ni
95,96
10CrMo910
0%
10 %
20 %
30 %
40 %
50 %
2,24
60 %
70 %
80 %
90 %
Finnish Swedish Flame Days, January 28-29, Naantali
100 %
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Results
Measurements of the oxide layer thickness (10CrMo9-10 steel)
Run
Fuel
1
2
wp+0.1
wp+0.5
2’
3
4
5
6
7
80
Exp.
time[h]
Probe
temp.
[ºC]
wp+0.5
28
7
7
550
wp+0.5
wp+0.5
wp
wp
wp
7
7
7
7
7
500
450
550
500
450
450
550
Oxide layer thickness [µm]
0º
45º
180º
8
40
43
18
73
37
10
47
17
25
7
22
3
9
4
Results under evaluation
70
60
50
40
30
20
10
180°
45°
0°
0
450, 28h,
0.1
550, 7h,
0.5
550, 7h,
0.5
500, 7h,
0.5
450, 7h,
0.5
10
Wood pellet doped with 0,1% ZnCl2, 28h-exposure time, 450ºC-probe temp.
18,98µm
windward
:
10CrMo9-10 steel ring
Steel test ring
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Wood pellet doped with 0,1% ZnCl2, 28h-exposure time, 450ºC-probe temp.
80,0
60,0
40,0
area 4
20,0
area 5
10CrMo9-10 steel ring
Na2O
MgO
Al2O3
SiO2
P2O5
SO3
Cl
K2O
CaO
TiO2
Cr2O3
MnO
Fe2O3
ZnO
0,0
5
4
Wood pellet doped with 0,5% ZnCl2, 7h-exposure time, 500ºC-probe temp.
ZnO, Zn, ZnCl2
4
KCl
Fe2O3
10CrMo9-10 steel ring, 45º
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Wood pellet doped with 0,5% ZnCl2, 7h-exposure time, 550ºC-probe temp.
Sanicro 28 steel ring, 45º
element
at %
O
60.2
Cl
7.53
K
1.59
Ca
0.99
Cr
8.99
Fe
14.80
Ni
4.76
Zn
1.32
Total
100
2
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Wood pellet doped with 0,5% ZnCl2, 7h-exposure time, 550ºC-probe temp.
windward
leeward
50,0
wt. %
40,0
30,0
Wind
20,0
Lee
10,0
0,0
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Conclusions
•
Preliminary Test results showed that ZnCl2 has a profound impact on high
temperature corrosion
•
Higher ZnCl2 concentrations in the fuel resulted in higher corrosion rates of low
alloy steel
•
Oxide layer formed on the high alloy steel was negligible
•
Zn was mainly found as ZnO on the windward side of the corrosion probe but
there are also indications for ZnCl2, which implies that ZnCl2 has not totally
decomposed during the combustion process.
•
Corrosion rate on the high grade steel seems to be negligible under the tested
conditions and exposure times.
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Acknowledgements
TUM stuff for assistance with the experiments and making
available the test facility
Funders:
INECSE – Marie Curie Early Stage Training Programme,
Chemcom,, a mainly Tekes financed project at the Process Chemistry
Chemcom
Centre at Åbo Akademi University. Other funders were: Andritz Oy
Oy,, Foster
Wheeler Energia Oy
Oy,, International Paper Inc., Metso Power Oy
Oy,,
Oy Metsä
Metsä--Botnia Ab
Ab,, Clyde Bergemann GmbH, and UPMUPM-Kymmene Oyj
Oyj..
Thank you
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