Al2O3-ZrO2-TiO2 new promising refractory lining materials...

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.

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

3

Introduction

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)

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

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

7

Investigation of new Al2O3-ZrO2-TiO2-

refractories


8

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


9

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


10

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


11

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)


12

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


13

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)


14


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


15


slag infiltration through open pore

channels

Ti and Fe detectable in slag

formation of (Mg,Fe)Al2O4 spinel at

slag line

16

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

17

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

Al2O3-ZrO2-TiO2 new promising refractory lining materials...

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