Brick – Classification Speaker's name Décembre 2007 4 Refractory brick definition : Refractory products are ceramic materials which have a refractoriness above 1500°C. There are mainly composed of oxides (SiO 2 , Al 2 O 3 , CaO, MgO, Cr 2 O 3 & ZrO 2 ) and/or non-oxides (SiC …) Raw material fineness A Raw material fineness B Raw material fineness C Developed bonding Bricks are a mixture of different particles / powders. Cohesion of the material is made by a sintered process.
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LMM Training session - WordPress.com · 2012-10-15 · Bricks are a mixture of different particles / powders. Cohesion of the material is made by a sintered process. Brick – Classification
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Brick – Classification
Speaker's name Décembre 2007 4
Refractory brickdefinition :
Refractory products are ceramic materials which have a refractoriness above 1500°C.There are mainly composed of oxides (SiO2, Al2O3, CaO, MgO, Cr2O3 & ZrO2) and/or non-oxides (SiC …)
Raw material fineness A
Raw material fineness B
Raw material fineness C
Developed bonding
Bricks are a mixture of different particles / powders. Cohesion of the material is made by a sintered process.
Brick – Classification
Speaker's name Décembre 2007 5
Refractory brickSintered process :
The sintered process consists to heat up a powder without reaching the melting point. Under heat effect, the particles link together creating a ceramic bonding and give the cohesion to the brick.The sintered process is used to achieve the ceramic material densification :
•The process allows to control the material densification. As we start with a powder and the fact that the powder does not melt, we can control the particles size, the material density, depending on the initial pressure level applied to the material and/or doping products, binders addition.
•The process allows to obtain hard but fragile material with a controlled porosity.
•The process allows to master volumetric dimensions of the bricks. As there is no state changes, the volumetric dimension variations are minimum compare to a fused process (shrinkage phenomena).
Refractory workshop – Brick Selection
Speaker's name October 2006 - 11
What are the requirements?Heat resistance Must keep good insulation and protective
qualities over a wide range of temperature
Chemical corrosion resistance
Must resist reacting with the load and products of combustion
Cold mechanical strength Must withstand transport and installation
Hot mechanical strength Must have a good resistance to wear and load abrasion
Dimensional stability over awide range of temperature
Expansion or shrinkage can compromise lining structure
Very small thermal conductivity
Low installed cost
Must reduce wall heat losses, yet promote coating formation
Poor quality or poorly installed refractory is VERY expensive
Presenter
Presentation Notes
Clinkering temperature ³1450°C Losses per wall on the kiln @ 1 calorie/m in length per ton of clinker (the KT may, depending on the country and the use or non-use of alternative fuels, cost 0 to 9 USD) Cooling, heating and crusting can provoke shocks Clinker is abrasive Shell deformation excessive play at the band Alcali attacks, free K2O Elastic deformation Expansions are not the same at the suction and intradoss In France, it is the 4th item of expenditure 800 g/t of clinker 3,50 FF/t of refractory clinker 1,50 FF/t of clinker in M.O.
Refractory workshop – Brick Selection
Speaker's name October 2006 - 12
Brick or castable? - Advantages• Brick
• Constant & homogeneous properties
• Low risk of defects in lining• Self-supporting lining• Quick heating up possible
• Castable• Very good product
properties• Quick & easy lining method• Reduction of
downtime/stoppage• Lower costs in case of
stoppage• Very versatile
• Can adapt to just about any shape or size
Refractory workshop – Brick Selection
Speaker's name October 2006 - 34
Intrinsic characteristics
• Thermal conductivity (W/m.K)
The coefficient of thermal conductivity is a measure of a material’s capacity to transfer heat.
The greater the coefficient of thermal conductivity, the greater the material’s capacity to transfer heat. The greater the coefficient of thermal conductivity, the hotter the walls, the greater the heat loss via the walls.Conversely, the lower the thermal conductivity the greater the material’s insulating capacities.
Thermal conductivity also has an affect on the material’s capacities to resist tothermal shock. When there is thermal shock, materials with high levels ofthermal conductivity offer less resistance to the transmission of heat throughoutthe body of the material. The greater the coefficient of thermal conductivity,the greater the resistance to thermal shock.
Presenter
Presentation Notes
Thermal conductivity expressed in w, m-1, O°K - depends on the material - varies with the temperature except for certain very cristalized products (chrome magnesium) and spinel magnesium - used to measure lining thickness Softening under load in% Deformation following a given rise in temperature Thermal shock resistance Number of cycles between 2 given temperatures e.g. 50 cycles of 950°C to 18°C
Refractory workshop – Brick Selection
Speaker's name October 2006 - 71
Brick size / format
• Standard
a = Cold faceb = Hot faceh = Height ou thicknessL = Length
E.g.: 320, 620
D
b
a
h L
Refractory workshop – Brick Selection
Speaker's name October 2006 - 50
Types of BricksInsulating
Alumina 40%- 50%
Alumina 60%- 75%
Alumina 75%- 85%
Dolomite
Magnesia - Chrome
Magnesia - Spinel
Magnesia hercynite - Spinel
Refractory workshop – Brick Selection
Speaker's name October 2006 - 51
Chemical Analysis
SiO2 65 - 69Al2O3 22 - 26Fe2O3 2.5
Not recommended by TCEA
Application Advantages LimitationsCalcining zone Excellent insulating
propertiesMust not be extended to
the safety zone (Too high T° for this brick)
Poor resistance to abrasion
Very poor alkali resistance
Lightweight Very poor resistance to mechanical stress