al2o3-zro2-tio2 new promising refractory lining materials...
TRANSCRIPT
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Al2O3-ZrO2-TiO2 – new promising refractory
lining materials for slagging gasifiers
P. Gehre*, C.G. Aneziris, M. Klinger, M. Schreiner
TU Bergakademie Freiberg | Institute of Ceramic, Glass and Construction Materials | Agricolastraße 17, 09599 Freiberg |
Phone: +49 3731 39-4254 | www.tu-freiberg.de | Dr. Patrick Gehre | 6th International Freiberg Conference | 20.05.2014
20th May 2014, 6th International Freiberg Conference on IGCC & XtL
Technologies, Dresden/Radebeul, Germany.
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Outline
2
Introduction
Wear mechanisms in slagging gasifiers
Wear of high-chrome oxide materials
Development of chrome oxide-free refractories
Al2O3-ZrO2-TiO2-refractories
Experimental
Thermomechanical properties
Corrosion resistance
Field test in a slagging gasifier
Summary
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3
Introduction
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Introduction
4
Wear mechanisms in slagging gasifiers
temperature
T = 1300 – 1600 °C
thermal cycling
pressure
p = 20 – 40 bar
atmosphere
H2, CO, H2O(g), CO2, H2S, NH3
abrasion
coal and ash particles / hot process gases
ash / slag
corrosionCO·H2 / slag
RHI AG
O2 + H2O (g)
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Introduction
5
Wear of high-chrome oxide materials
* J.P. Bennett, K.-S. Kwong, Failure mechanisms in high chrome oxide gasifier refractories, Metallurgical and Materials
Transactions 42A (2011), pp. 888-904
SEM of slag/refractory interphase after 2000 h at
1500 °C with coal slag*
1 – slag
2 – FeAl2O43 – FeO·Cr2O34 – Cr2O3-Al2O3-grain
5 – slag filled pore
6 – slag/refractory interphase
no dissolution of refractory brick
infiltration by CaO, SiO2 and alkalis
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Introduction
6
Development of chrome oxide free materials
State of the art – Cr2O3-MgO / Cr2O3-ZrO2-Al2O3
• poor service life of 3 – 24 months
• high costs, supply issues and potential for toxic chrome(VI)
oxide formation, recycling issues
Chromia trend
• Cr2O3 + P / Cr2O3 + C
Alumina based refractories
• good mechanical properties at high temperatures
• widely available and cheep
• lining for low temperature gasification processes
• but: corrosion by molten slag above 1400 °C
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Investigation of new Al2O3-ZrO2-TiO2-
refractories
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Al2O3-ZrO2-TiO2-refractories
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Experimental
A1650 AT2.5 AZ5.0
Composition (wt.%)
Tabular alumina 88.0 85.5 83.0
Reactive alumina 9.0 9.0 9.0
Hydratable alumina 3.0 3.0 3.0
Titania (TiO2) - 2.5 -
Zirconia (ZrO2) - - 5.0
Additives 1.0 1.0 1.0
• mixture of the raw materials with water (self flow castables)
• casting, drying and sintering at 1650 °C
• investigation of thermomechanical properties, corrosion resistance
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Al2O3-ZrO2-TiO2-refractories
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Thermomechanical properties
OP (%) CMOR (MPa) HMOR (MPa)Loss of CMOR
after TS* (%)
A1650 14.2 32.3 18.0 29
AT2.5 14.9 27.0 2.8 19
AZ5.0 15.8 25.5 23.3 16
ZirchromTM 60** 13.4 28.0 5.0 68
AT: increase of thermal shock resistance but critical low HMOR
AZ: good thermal shock resistance and high HMOR
* 800 °C with pressurized air
** L. San-Miguel, C. His, M. Schumann, High performance refractories for gasification reactors, refractories
WORLDFORUM 3 (2011), pp. 95-100
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Al2O3-ZrO2-TiO2-refractories
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Corrosion resistance – “cup test”
A1650 completely infiltrated by slag
AT2.5 and AZ5.0 show very low slag infiltration, no dissolution or crack
formation
1450 °C, 3 h in 100 % CO-atmosphere with acidic brown coal ash
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Al2O3-ZrO2-TiO2-refractories
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Corrosion resistance – SEM of AT2.5
infiltration through open pores
formation of dense MgAl2O4-layer
reaction of MgO (slag) with Al2O3
but: no MgAl2O4 layer on A1650
→ 2 possible explanations:
a) TiO2 promotes in situ spinel
formation*
b) minor TiO2 solution increases slag
viscosity
* A. Samanta et al., Taikabutsu Overseas 31 (2011)
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Al2O3-ZrO2-TiO2-refractories
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Interaction of AT2.5 with slag – TOM-AC*
brown coal and gasifier ash (4 g) pellet on refractory disc (Ø 50 mm)
*TOM-AC – thermo-optical microscope with atmosphere control
10 K/min → 1450 °C in Ar/H2 (5 %)
Component
(wt.%)Coal ash Gasifier ash
SiO2 40.21 22.51
Al2O3 18.40 8.07
CaO 9.43 27.89
Fe2O3 7.17 7.97
MgO 5.20 5.56
Na2O 5.12 0.29
SO3 5.05 2.43
K2O 3.39 6.72
Trace 6.03 18.56
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Al2O3-ZrO2-TiO2-refractories
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Interaction of AT2.5 with coal and gasifier slag
glassy slag on
top
spread on the
surface
(residual iron
droplet)
no infiltration /
MgAl2O4-layer
→ confirms the
results gained
under CO
reaction front
(white rim),
formation of
needle shaped
CA-phases
(CA2)
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Al2O3-ZrO2-TiO2-refractories
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Field test in a slagging gasifier
Siemens Fuel
Gasification Test Centre
capacity: 5 MWth
reactor type:
entrained-flow with cooling
screen
Schema of Siemens Fuel Gasifier, Siemens AG
Head of Siemens Gasifier, Siemens AG
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Al2O3-ZrO2-TiO2-refractories
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Field test in a slagging gasifier
slag infiltration through open pore
channels
Ti and Fe detectable in slag
formation of (Mg,Fe)Al2O4 spinel at
slag line
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Conclusions
“Al2O3-ZrO2-TiO2 – new lining materials for slagging gasifiers”
Material properties
Al2O3 with TiO2-addition: good thermal shock resistance but critical low HMOR
Al2O3 with ZrO2 shows good thermal shock resistance and high HMOR
Corrosion (cup test, TOM-AC, field test)
AT2.5 and AZ5.0 show marginal slag infiltration, no dissolution or crack formation
in situ formation of dense MgAl2O4-layer stops corrosion (under testing conditions)
esp. TiO2 promotes MA-formation and increases slag viscosity
Ar/H2 (5 %): no corrosion with SiO2-Al2O3-rich coal ash
minor reaction with CaO-SiO2-rich gasifier ash (CA-phases)
field test: marginal slag infiltration; formation of (Mg,Fe)Al2O4 spinel
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Thank you for your attention!
“Al2O3-ZrO2-TiO2 – new lining materials for slagging gasifiers”
Acknowledgment
This publication has been funded by the German Centre for Energy Resources, support
code 03IS2021A. We would like to thank the Federal Ministry for Education and
Research (BMBF) and our partners from the industry for funding this project.
TU Bergakademie Freiberg | Institute of Ceramic, Glass and Construction Materials | Agricolastraße 17, 09599 Freiberg |
Phone: +49 3731 39-4254 | www.tu-freiberg.de | Dr. Patrick Gehre | 6th International Freiberg Conference | 20.05.2014