Refractory in Cement Industry Wear Phenomena
Wear
Phenomena
Refractory In Cement Industry
Wear of refractories,
particularly when using
waste fuels and their
influence on the brick
life
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Refractory in Cement Industry Wear Phenomena
Influences on the part of
the cement producer Refractory
Installation
storage Thermal
Kiln Chemical
Lifetime of Burning
Refractory Refractory Conditions
selection
Mechanical
installation Raw Influences on the
draw Production Material part of the producer
Quality Quality
Thermal Influences
Typical burning conditions
Clinker melt infiltrations
Concave / Sloping
erosion
Thermal shocks
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Refractory in Cement Industry Wear Phenomena
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
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Refractory in Cement Industry Wear Phenomena
Concave/sloping/smooth hot surfaces
(brickwork erosion)
constant thermal overloading of the brickwork lava-like
coating
Concave/sloping erosion
(brickwork erosion)
direct flame impact
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Refractory in Cement Industry Wear Phenomena
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
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Refractory in Cement Industry Wear Phenomena
Salt infiltration:
Volatile elements and their Principal Compounds
(without heavy elements)
Sulphur compound
SO2 , SO3 , S2-
Potassium Oxide
K2O
Chorine
Cl2 , Cl-
Salt infiltration : alkali sources
Kiln feed raw material
Clay and mica minerals
Feldspar minerals (Na,K)AlSi3O8
Additives (ashes, bentonite, etc.)
Alternative combustibles
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Refractory in Cement Industry Wear Phenomena
Salt infiltration : Chlorine sources
Coal 0.1 – 0.3 % Cl
Lignite 0.1 - .013 % 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
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Refractory in Cement Industry Wear Phenomena
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
1< 1 <1
KCl + K2SO4 + SO 3 Free KCl + K2SO4 KCl + K2SO4 + K2O Free
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Refractory in Cement Industry Wear Phenomena
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)
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Refractory in Cement Industry Wear Phenomena
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
١٠
Refractory in Cement Industry Wear Phenomena
Silicate corrosion, sulphurs of sulphur in kiln atmosphere
(ASM <1)
Silicate corrosion reduces the
refractoriness and the structural
flexibility
Possibly operational difficulties in the kiln system & to
the clinker composition (ASM <1)
Formation of coating rings
and/or build-ups in the calcining
zone, inlet section, cyclones etc.
caused by the formation of
anhydrite (CaSO4 ), double
sulfate salts(calcium langbeinite,
syngenite),and spurrite phases
(sulfate spurrite).
١١
Refractory in Cement Industry Wear Phenomena
Possibly operational difficulties in the kiln system and to
the clinker composition (ASM <1)
Sulphur will be retained as sulfates in the clinker (approach or
exceed 2 %), reducing the add of gypsum at the clinker grinding
stage. The retarding of hydration and setting of cement will be
changed.
Formation of dusty clinker Reduction of the viscosity of clinker
melt and the surface tension of the liquid phases, which results
in clinker structure loosening, and a greater proportion of clinker
dust is formed.
Redox burning conditions
Local reduction and/or redox burning conditions caused by
incomplete combustion of fuels (coarse coal, ashes on the
lining’s surface)
Basic brick grades with alpine magnesia (crystalline magnesia)
are sensitive to the high Fe2O3 content
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Refractory in Cement Industry Wear Phenomena
“Alkali Spalling“
Thin hot face spallings due to brittleness of the brick texture
Alkalis react with the brick components from fireclay and high
alumina bricks forming alkali alumina silicates (feldspar,
feldspathoids). This formation is accompanied by volume
increase.
alkali spalling due to the
wear by alkalis
formation of new
minerals
alumina content, refractoriness, mechanical
resistance
Kiln shell corrosion
Migration and efflorescences of salts between brickwork and
kiln shell
Chemical attack of salts under kiln operating conditions (high
thermal corrosion)
Depending on the alkali-SO3 -ratio and oxygen partial pressure
bi- and trivalent iron oxides and/or iron sulphides are formed.
١٣
Refractory in Cement Industry Wear Phenomena
Hydration
Cracks from the brick surface into the brick‘s internal texture
Basic bricks are sensitive to humidity and must be stored and
protected against humidity, rain and sea water.
MgO reacts with water to brucite (Mg(OH2) ) which is
accompanied by volume increase (~ 53%).
Tropical/sub-tropical climate conditions accelerate this reaction.
Hydration
١٤
Refractory in Cement Industry Wear Phenomena
Mechanical Influences
Thermal expansion
Loosenings of the lining
Kiln shell deformation (ovality)
Groove in the lining
Pressure loads on the kiln
retaining ring
Thermal Expansion
Convex spallings on the
longitudinal joints
Too little allowance for
expansion leads
to higher pressure within the
brickwork.
Convex spallings finally occur.
Insufficient expansion space
Frequent kiln stops after the
burnout of the cardboards
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Refractory in Cement Industry Wear Phenomena
Loosenings of the lining
Loosenings of the brickwork due to brickwork movements
Spiral twisting, tilting of bricks, shearing cracks, abrasion
marks on the brick‘s cold face
Wrong installation, frequent kiln stoppages, kiln shell
deformations and ovalities
Kiln shell deformation (ovality)
Local strong spallings in the tire section, the surrounding
brickwork is intact. Increased ovality in the tire section
causes tensions and loosenings of the lining.
The brick‘s hot face is more loaded (spallings).
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Refractory in Cement Industry Wear Phenomena
Groove formation
Increased wear parallel to the kiln axis caused by groove
formation, the other brickwork is intact (spallings of 2 - 3
brickwork width)
Brickwork rings are closed too tightly, damage of the key bricks
using a wrong hammer
More than one iron plate within the brickwork rings
High pressure on the retaining ring section
Increased pressure of the brickwork onto the retaining ring.
Shearing tensions occur within the brickwork leading to cracks
and spallings of brick parts.
Instable, deformed kiln shell or ovality increases this wear.
١٧
Refractory in Cement Industry Wear Phenomena
Wear Influences onto
the Monolitic lining
Vapour explosion
monolithic Thermal
wear
influences
Mechanical
influences
Chemical
influences
Wear Influences onto the
monolitic lining
Vapour explosion (100 °C to ~600 °C)
Too fast heating up during setting/hardening and after heating up
of the monolithic lining
Thermal influences
Thermal shocks, thermal overloading, thermal spots
Chemical influences
Reaction with the kiln feed (clinker dust), thermochemical attack
by harmful components (alkali and sulfur compounds)
Mechanical influences
Abrasion, dust erosion (clinker dust), influences due to anchor,
kiln shell and metallic construction
١٨
Refractory in Cement Industry Wear Phenomena
Vapour explosion (100 °C to ~600 °C)
Riser shaft to
Cooler banks
calcinator/inlet chamber
Thermal influences
Cooler banks
(tension cracks caused by thermal shock)
١٩
Refractory in Cement Industry Wear Phenomena
Chemical influences
Kiln hood back wall
(alkali attack -> alkali spalling)
Chemical influences
Corrosion of metallic anchors
٢٠
Refractory in Cement Industry Wear Phenomena
Mechanical influences
Damper in the tertiary air duct
(high abrasion caused by strong air stream)
Mechanical influences
Embrittlement of metallic anchors
(formation of sigma phase)
٢١
Refractory in Cement Industry Wear Phenomena
Thermal, chemical and mechanical influence
Burner lance
A change of refractory wear, particularly when
using alternative or waste fuels in the cement
rotary kiln
Fuel oil and gas as primary energy since approx. 1960
Changeover to coal after the petroleum crisis in 1973/74
Use of alternative fuels since mid eighties
٢٢
Refractory in Cement Industry Wear Phenomena
Lining and coating zone of kilns using oil & gas
Outlet Burning Safety
zone zone zone
Coating in the burning zone
The magnesia-chromite bricks used in the hot zones and the
high alumina and fireclay bricks in the other sections perform
good regarding lifetime and wear resistance
A change of refractory wear, particularly when
using alternative or waste fuels in the cement
rotary kiln
Fuel oil and gas as primary energy since approx. 1960
Changeover to coal after the petroleum crisis in 1973/74
Use of alternative fuels since mid eighties
٢٣
Refractory in Cement Industry Wear Phenomena
Lining and coating zone of kilns using coal & Fuel oil
Outlet Lower Upper Safety
Burning
zone Transition Transition zone
zone
zone zone
Coating in the burning zone and particularly in the transition
zones
Magnesia-chromite bricks in the burning zone showing a usual
wear
Reduced service life of the magnesia-chromite lining in the
transition zones (salt infiltration, formation of alkali chromates,
redox burning conditions)
Salt infiltrations, alkali chromate formation and reducing
burning conditions in case of magnesia-chromite bricks
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Refractory in Cement Industry Wear Phenomena
Development of magnesia -Spinel & Magnesia-Zirconia Bricks
MAGPURE®93/95 ALMAG®A1 ALMAG SLC® REFRAMAG®85
ALMAG®85
FERROMAG®90
MAGNUM®95 MAGNUM®S
Main properties:
high resistance to alkali attack (no corrosion of the MA spinel
or the zirconia)
insensitive to reducing or redox conditions
A change of refractory wear, particularly when
using alternative or waste fuels in the cement
rotary kiln
Fuel oil and gas as primary energy since approx. 1960
Changeover to coal after the petroleum crisis in 1973/74
Use of alternative fuels since mid eighties
٢٥
Refractory in Cement Industry Wear Phenomena
Lining and coating zone using fuel with 50% & 50%
alternative fuel
Outlet Lower Transi Safety
Burning tion Burning Transition
zone Transition zone zone zone
zone zone
zone
Complex and instable coating situation and various flames
Lining lifetime clearly reduced, particularly in the transition
zones(massive salt infiltrations, local overheating, local redox
burning conditions)
Influence of secondary fuels on the refractory lining
and kiln system
Stronger chemical and physical attack against the basic bricks
Risk of irregular temperature profile in the kiln (local thermal
overload)
Risk of formation of local reducing atmosphere
Stronger chemical attack against the aluminous and fireclay
bricks
Stronger attack against the kiln/cyclone shell and the anchor
system
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Refractory in Cement Industry Wear Phenomena
Percentage of the different wear types
Up-to-date studies show that more than 60 % of the wear
cases are caused by salt infiltrations (alone or in combination
with other attacks)
23 % thermochemical Influences & Salts
23 % mechanical / thermomechanical % 60 <
influences and salts
17 % salts
23 % overheating
8 % mechanical/thermomechanical influences
1 % redox conditions
5 % other
Quaternary System : K2So4 – CaSO4 , KCl – CaCl2
٢٧
Refractory in Cement Industry Wear Phenomena
Increase of salt infiltrations and accumulation of other
harmful substances in the structure, balanced alkali-
sulphate modulus (ASM ~1)
Increase of salt infiltrations and accumulation of other
harmful substances in the structure, balanced alkali-sulphate
modulus (ASM ~1)
Use of alternative additives with the kiln feed
(e. g.: condensation of lead sulfide (PbS))
٢٨
Refractory in Cement Industry Wear Phenomena
Silicate corrosion , Surplus of sulphur in kiln
atmosphere (ASM <1)
refractoriness and the structural
flexibility are reduced
Influence of secondary fuels on the refractory lining and
kiln system
Stronger chemical and physical attack against the basic bricks
Risk of irregular temperature profile in the kiln (local thermal
overload)
Risk of formation of local reducing atmosphere
Stronger chemical attack against the aluminous and fireclay
bricks
Stronger attack against the kiln/cyclone shell and the anchor
system
٢٩
Refractory in Cement Industry Wear Phenomena
Local overheating and redox burning conditions
Redox burning condition & salt infiltration
٣٠
Refractory in Cement Industry Wear Phenomena
Strong reducing and redox burning conditions
carbon disintegration, Boudouard reaction (CO + C <-> 2CO)
2
carbon
horizon
Influence of secondary fuels on the refractory lining
and kiln system
Stronger chemical and physical attack against the basic bricks
Risk of irregular temperature profile in the kiln (local thermal
overload)
Risk of formation of local reducing atmosphere
Stronger chemical attack against the aluminous and fireclay
bricks
Stronger attack against the kiln/cyclone shell and the anchor
system
٣١
Refractory in Cement Industry Wear Phenomena
“Alkali Spalling“ in the aluminous bricks
Structural embrittlement and spalling of thin layers.
The alkalis react with the components of fireclay and
aluminous bricks under formation of alkali containing alumina
silicates (feldspars, feldspathoids).
This formation is accompanied by a volume increase.
Influence of secondary fuels on the refractory lining
and kiln system
Stronger chemical and physical attack against the basic bricks
Risk of irregular temperature profile in the kiln (local thermal
overload)
Risk of formation of local reducing atmosphere
Stronger chemical attack against the aluminous and fireclay
bricks
Stronger attack against the kiln/cyclone shell and the anchor
system
٣٢
Refractory in Cement Industry Wear Phenomena
Effect of kiln shell corrosion and cyclone steel shell
Corrosion of metallic anchors (refractory areas installed with
castables), formation of alkali chromate (K2 CrO3 ), surplus of
alkalis in kiln atmosphere (ASM >1)
٣٣
Refractory in Cement Industry Wear Phenomena
Alkali chromate consideration in magnesia spinal lining
Arcanite
(blue efflorescences)
Arcanite
(green efflorescences)
alkali
chromate
Requirements to refractory material and its installation
In Cement Rotary Kilns fired with secondary fuels
Minimization of infiltration and corrosion of refractory
components
Optimization of the structural texture by higher flexibility and
high structural strength
Renewable sealing of the refractory’s hot face
Optimization of installation technology, especially in the static
area of cement kiln system including a flexible and fast
installation of high grade refractory concretes and bricks
Innovative insulating and protection options for the anchoring
system and steel shell to reduce or even prevent different
corrosion mechanism of shell and anchor
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Refractory in Cement Industry Wear Phenomena
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