Basic bricks

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GLOBAL TRENDS IN THE CEMENT MAKING PROCESS
UNITECR 2009, Salvador - Brazil
Adam A. WajdowiczOctober 2009
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Challenges of the cement global industry

• Reduce energy consumption
• Increase the use of alternative fuels
• Use of alternative raw materials without changing
  clinker quality- materials recycling
• Reduce emissions of CO2 setting targets to
  reduce greenhouse gas emissions
• Great concern how to protect the environment .
• Strong research in the sphere of sustainability

Gt26
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MARKET ENVIRONMENT GLOBAL CRISIS

• Some countries have been badly affected like USA,
  Ireland, Spain, UK.
• Africa and Middle East lost 10 in some countries
  
• In central Europe the loss of production varies
  from 10 to 40 in some countries.
• Many old wet process kilns have been discontinued
  for ever.
• Whoever will be not able to reach 70 of
  substitution of energy source via alternative
  fuels and raw materials will be not competitive.
• On average 40 substitution is a reality in
  Europe, Asia, North America and South America.
• Right now many European countries are targeting
  88 substitution rate.

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Present reality

• Simultaneous grinding of coal and pet coke lead
  to a variable grain size once the Hardgrove index
  is different. Coarser grains of pet coke with
  more than 90 micron sieve tend to burn at very
  upper transition zone.
• This causes the appearance of double or triple
  flame affecting coating distribution and the kiln
  thermo-chemical gradient.
• Coal ash has to be ground sufficiently fine and
  injected sufficiently far into the kiln to make
  sure that it will be incorporated into the raw
  meal.
• Coarse ash particles and those projected
  insufficiently far into the kiln fail to combine,
  giving higher levels of free lime .
• Liquid waste with variable amounts of water and
  varying heat value make the flame to be non
  predictable and impinging on the refractories,
  index
• Burning of chlorinated plastics and solvents
  without continuity.
• Sudden increase in burning zone thermal load
  (new coolers, new burners)
• Variable degree of precalcining at the kiln inlet

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Impact on the process

• More frequent ring and buildup formation
• Imbalances in Sulfur/alkali ratio
• Frequent need to change the in kiln rotational
  speed.
• Increase in the number of cold stoppages
• Low alkali clinker, oil well clinker, off-white
  clinker, etc
• More wear at kiln tire stations specially if
  clinker is dusty.
• Very difficult to specify the right brick as
  someone has to decide if the brick should
  encourage coating development or avoid it!
• Variable coating development at the area of upper
  transition tire is a headache. This condition may
  cause the temperature to be hotter on one side of
  the shell than the other. This causes stress and
  torsional displacement of the refractories.

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More impacts on the process

• REPLACEMENT OF TRADICIONAL FUELS LIKE NATURAL
  GAS, PET COKE, OIL, RESIDUAL COAL, PAPER,
  PLASTICS, MEAT, BONE MEAT, BATTERY CASINGS, USED
  LUBRICANTS, WASTE SOLVENTS, SHREDDED TIRES,
  MUNICIPAL GARBAGE, ETC.
• THE USE OF ALTERNATIVE FUELS AT THE RISER DUCT IS
  MORE DIFFICULT IN THE SATTELITE COOLER KILNS ONCE
  THE DRAFT AND OXIGEN COULD BE NOT ENOUGHT TO BURN
  THEM PROPERLY. USUALLY IS LIMITED TO 20-25 OF
  SUBSTITUITION.
• LONGER FLAMES AND LOW HEATING VALUES REQUIRE MORE
  FUEL AT THE BURNING ZONE TO MAKE SURE THAT FREE
  LIME IS LOW. THAN THERMAL LOAD EXCEEDS 5 x106
  Kcal/m2.h. USUALLY IT IS HARD TO GET A STABLE
  COATING.

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ROTARY KILN ZONES
BURNING ZONE
UPPER TRANSITION
LOWER TRANSITION

• EXCELLENT FLEXIBILITY
• HIGH RESISTANCE AGAINST INFILTRATION ALKALIES
  SALTS
• HIGH RESISTANCE AGAINST CHEMICAL CORROSION BY
  CLINKER LIQUID
• PHASES AND SO3 AND OR ALKALI SALT VAPORS.

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Different kiln zones and types of wear
ZONE 1 POTASSIUM CHLORIDE INFILTRATION,
CONDENSATION ZONE 2 POTASSIUM SULFATE
INFILTRATION, CONDENSATION ZONE 3 UNSTABLE
COATING, BRICK EROSION, MECHANICAL STRESS ZONE 4
PEAK TEMPERATURE, CLINKER MELT INFILTRATION,
REDOX, COATING PULL ZONE 5 FLAME IMPINGEMENT,
UNSTABLE COATING, BRICK EROSION, MECHANICAL ZONE
6 ABRASION, THERMAL SHOCK, ALKALI INFILTRATION,
BRICK RETAINER
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DAY AND NIGHT CaO TENDS TO SATURATE THE CERAMIC
BRICK MATRIX
350ºC
1450ºC
KCl Alkali
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MAJOR MINERALOGICAL PHASES ACCESSORY PHASES

• BASIC BRICK
• MgO
• MgO.Al2O3
• DOLOMA
• ZrO2
• Hercynite
• C2S, C3S
• M2S, CMS, C3MS2
• C12A7
• 3CaO.3Al2O3.CaSO4
• MgO.Fe2O3
• K2Mg2(SO4)3
• K2SO4
• KCl, NaCl
• Phase Q-C20Al26Mg3O68

• CLINKER
• C3S
• C2S
• C3A
• C4AF
• CaO
• ALKALI,
• Sulfates
• Fluorine
• Etc.

MAJOR
ACCESSORY
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LIME SATURATION FACTOR

• KÜLL DEVELOPED AN EQUATION THAT DEFINES THE
  MAXIMUM QUANTITY OF LIME COMBINED WITH SiO2,
  Al2O3, AND Fe2O3
• THEN LSF SHOWS THE LIME EFFECTIVELY SATURATED AT
  1450ºC IN A KIND OF FROZEN EQUILIBRIUM
• FREE LIME IS THE LIME THAT CANNOT BE COMBINED.
• IF FREE LIME IS TOO HIGH IT WILL BE AVAILABLE TO
  SATURATE REFRACTORY MINERALS TO DEVELOP NEW
  SILICATES. THIS IS THE MATRIX CORROSION.

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TYPICAL KILN CONSTRAINS

• LIQUID PHASE CORROSION
• THERMAL OVERLOAD THAT DRASTICALLY REDUCES LIQUID
  PHASE VISCOSITY
• LIQUID PHASE INFILTRATION
• HIGH KILN SHELL TEMPERATURE BUT WITH CONDITIONS
  TO DEVELOP AND KEEP A SOUND AND STABLE COATING
  
• HIGH KILN SHELL TEMPERATURE WITHOUT ANY CHANCE TO
  GET COATING
• MECHANICAL STRESS - OVALITY - POOR ALIGNMENT
• ALKALI SULFATES
• ABRASION RESISTANCE
• THERMAL LOAD
• REDUCING ATMOSPHERE
• SHIFTING CLINKER TYPES 2 TO 3 TIMES PER MONTH

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TYPICAL CONSTRAINTS IN ROTARY KILNS
WHERE TO WORK OUT
BRICK PROPERTIES

• SELECTION OF RAW MATERIALS EXEMPT OF B203,
  Fe203, SiO2
• REDUCED, SMALL AVERAGE DIAMETER OF
  PORES-CORROSION RESISTANCE OF THE SPINEL GRAIN
• LOW PERMEABILITY
• SELECTION OF RAW MATERIALS THAT FAVOUR THE
  COATING ADHERENCE -REDUCE THE SURFACE TENSION
• CHOICE OF RAW MATERIALS THAT REDUCE THE THERMAL
  CONDUCTIVITY
• CHOICE OF SECUNDARY AGGREGATES WITH LOW E.M.
• HIGH COLD CRUSHING STRENGTH
• HIGH REFRACTORINESS
• LOW Fe2O3 CONTENT

LIQUID PHASE RESISTANCE THERMAL
SHOCK RESISTANCE THERMAL CONDUCTIVITY ALKALI
RESISTANCE PERMEABILITY ELASTIC
MODULUS COATING BEHAVIOUR
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How do you see this graph ?
Very interesting but my eyes can only see
CLINKER
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BURNING
CALCINATION
UTZ
LTZ
Limestone Clay Quartz CA C12A7 C2S Free
lime Spurrite
Free lime C2S C2F C3A C4AF C2AS LP1338ºC
C3S C2S C2AS C3A C4AF Free lime LP1450ºC
C3S C2S C3A C4AF Free lime
Raw meal
Clinker
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What are the most outstanding wear Mechanisms at
that part ?
Main facts ?Temperature from 50 to
950ºC ?Decarbonation is mostly concentrated in
the static preheater ?Presence of alkali
vapours If CO2 and SO2 are not removed at right
time then there is a risk to develop middle kiln
rings ?Brick melting if there is double flame
problem due to unburnt fuels Kiln shell corrosion
Then the ideal refractories should have Low
permeability Excellent resistance to alkali
attack Non wetting properties Low thermal
conductivity Al203 contend around 35 at
preheater And special fireclay alkali resistant
into the kiln
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What happens nowadays at upper transition zone?
If raw meal has big variability ?coating is
unstable The position of the appearance of
first liquid phase varies according to the fuels
type set up. Kiln shell temperature could vary
from 360ºC up to 410ºC If coating is unstable. As
a consequence an induced high kiln ovality maybe
present. Risk of brick spiralling. Serious and
unpredictable alkali salts infiltration
VA
Fuel
Brick properties required Low permeability Capab
ility to absorb as much as possible alkali
salts without the risk to exceed the maximum
acceptable elastic modulus
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What does it mean BURNING ZONE ?
MAIN WEAR MECHANISMS Thermal load Clinker liquid
phase corrosion Flame impingement Abrasion Unstabl
e coating Reducing atmosphere
C3S C2S C2AS C3A C4AF Free lime LP1450ºC
BASIC BRICKS THAT CAN OFFER RESISTANCE TO
CLINKER LIQUID PHASE CORROSION CAPABILITY TO
DEVELOP COATING THERMAL SHOCK RESISTANCE LOW
AVERAGE PORE SIZE RESISTANCE TO THE CLINKER TYPE
SHIFTING HIGH THERMAL LOAD WHENEVER PRODUCING
HARD TO BURN CLINKERS
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LOWER TRANSITION ZONE
Clinker abrasion Mechanical stress Shifting
coating MECHANICAL STRESS DUE TO THE TYRE
STATION WRONG DESIGN OF RETAININIG RINGS THERMAL
LOAD ALKALI ATTACK WITH KILNS WITH HIGH
EFFICIENCY COOLERS-SECONDARY AIR CLOSE TO 1200ºC
ALK
BASIC BRICKS MUST HAVE HIGH ABRASION
RESISTANCE RESISTANCE TO CLINKER LIQUID PHASE
CORROSION VERY LOW AVERAGE PORE SIZE LOW GAS
PERMEABILITY LOW ELASTIC MODULUS HIGH
FLEXIBILITY
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MAJOR PROBLEMS CAUSED BY THE THERMO-CHEMICAL
GRADIENT DISPLACEMENT
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Conclusions

• The present reality requires more research of
  refractories resistant to alkali vapors, sulfates
  and many other minor elements like fluorine,
  zinc, etc.
• Special refractories based on lime and MgO to
  resist thermal overload when shifting fuels or
  clinker types.
• Numerical simulation to determine the thermal
  mechanical behavior for refractories for cement
  kiln applications.
• Development of refractories with lower thermal
  conductivity to reduce thermal losses.

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MAIN WEAR MECHANISMS

• ALKALIES SALTS PHASES INFILTRATION 85
• CLINKER LIQUID PHASES INFILTRATION 10
• SLIGHT INFILTRATION
• MAYENITE PHASE FORMATION
• MEDIUM INFILTRATION
• Q PHASE FORMATION
• HEAVY INFILTRATION
• SILICATES PHASES MIGRATION
• YEELIMITE ( Y PHASE ) PHASE FORMATION
• MECHANICAL PROBLEMS 5

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• THANK YOU VERY MUCH FOR YOUR TIME!

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New Challenges for Refractorieswith 2D and 3D
Alternate Fuels
2Dand3D
RT2
Distribution of Thermal Energy Consumption of
Alternate Fuels - Germany
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FREQUENT FUEL CHANGES
COKE
COAL
C/H
BUNKER
DIESEL
WDF
GAS
CH4
H2
RT17
EMMISSIVITY
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Example big raw meal variability 30 running days
Rt 17
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Example of mag-spinel after one year at lower
transition zone of a kiln burning plastics and
some industrial residues
Rt 19