Wear Phenomena of Refractories

Wear of refractories, particularly when using waste fuels and their influence on the brick life Dr. Johannes Södje

Influences on the part of the cement producer Refractory installation

thermal

storage Lifetime of refractories

chemical kiln burning conditions mechanical

Refractory selection

Installation draw

Productionquality

Raw material quality Influences on the part of the producer

Stresses on the Refractory Lining in Rotary Cement Kilns

loads on refractory linings

Thermal influences

Typical burning conditions Clinker melt infiltrations Concave/sloping erosion Thermal shocks

Typical burning conditions

Clinker melt infiltration Densification of the brick‘s hot face caused by clinker melt infiltration increased thermal influences - variations of the kiln feed composition -

Concave/sloping erosion (brickwork erosion) constant thermal overloading of the brickwork direct flame impact coating free operating conditions with standard bricks with low refractoriness

Thermal shock influences Too fast heating up or cooling down Loss of coating Optimizing: Taking heating procedure into consideration/ cooling down slowly

Chemical influences Salt infiltration Corrosion of chrome spinel Silicate corrosion Redox burning conditions “Alkali Spalling“ Corrosion of the kiln shell Hydration of basic bricks

Salt infiltration: Volatile elements and their principal compounds (without heavy metals) Sulphur compound SO2, SO3, S2Potassium oxide K2O Sodium oxide Na2O Chlorine Cl2, Cl-

Salt infiltration: alkali sources

Kiln feed raw material Clay and mica minerals Feldspar (Na,K)AlSi3O8 Plagioclase (Na,Ca) (Si,Al) Al2Si2O8 Additives (ashes, bentonite, etc.) Alternative combustibles

Salt infiltration: chlorine sources

Coal

0.01 - 0.3 % Cl

Lignite

0.1 - 0.13 % Cl

Animal meal

0.6 - 1.6 % Cl

Plastics »PVC« 20 % of the worldwide production of»plastics« CH2=CHCl

30 % Cl

Salt infiltration: sulphur sources

Kiln feed raw material:

FeS2, PbS, ZnS, CaSO4, CaSO4·H2O

Oil

0.2 - 2.5 %

Pitch/Tar

1-6%

Coal

0.1 - 12 % SO3 in the ash

Petrol coke

5-8%

Lignite

0.2 - 15 % SO3 in the ash

Concentrations of salts in the cement kiln system Circulation of volatile compounds alkalis + Cl-

alkalis + SO2/SO3

Calculation of the alkali-sulphate modulus (ASM) in the cement clinker

K 2O Na2O Cl + − 62 71 ASM = 94 SO3 80

1

KCl + K2SO4 + K2O free

Salt infiltration, balanced alkali-sulphate modulus (ASM ~1) Densification of different brick horizons Infiltration of gaseous alkali chloride and/or sulfate components, condensation and densification of the brick texture Sulfate salts mostly in the lower transition zone and burning zone together with alkali chlorides in the upper transition zone

Salt infiltration, balanced alkali-sulphate modulus (ASM ~1)

Chrome spinel corrosion, surplus of alkalis in kiln atmosphere (ASM >1) Corrosion of chrome spinel in the presence of free alkalis at higher temperature Formation of toxic, hexavalent alkali chromate sulfate (yellow efflorescences = water soluble) Contamination of ground water, mason eczema

Silicate corrosion, surplus of sulphur in kiln atmosphere (ASM