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DESIGN OF FURNACE & REFRACTORY LINING
By
MK Maity (Materials & Corrosion Section, STC-J)
THE PERFORMANCE OF REFRACTORY LINING DEPENDS ON
Lining Design
Selection of Material
Installation
Operation Of Furnace
Maintenance
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OBJECTIVE OF A GOOD LINING DESIGN
Operation & Production At Optimum Cost & Expenses Of Refractories Used
To Obtain Optimum Trouble Free Service Life
To Have Reliable & Dependable Lining System
Ease Of Material Procurement
Ease Of Installation
Future Ease Of Maintenance
Ease Of Repair
33
DESIGN & DETAIL ENGINEERING
Detail Of Lining :• Materials Quality
• Thickness
• Heat Transfer Calculations
• Shape & Size Of Bricks , C.F.Modules, Etc.
• Dimensional Tolerances,
• Laying Pattern
• Lining Details Of Openings, Corners, Junctions
• Type Of Mortar & Mortar Joint
• Type Of Expansion Joint, Location & Width
4
DESIGN & DETAIL ENGINEERING
Detail Of Lining :Anchor & Hard-wares:
• Anchor & Support Quality
• Anchor Design , Dimension, Height
• Anchor Spacing & Orientation
• Vapor Barrier ( SS, Al foil)
• Corrosion Resistant Coating
5
DESIGN & DETAIL ENGINEERING
Refractory Materials:• Material Specifications & Test Methods• Quantity of Materials & Overages• Suppliers
Installation:• Installation Method• Sequence of Installation• Selection of Contractors• Lining Dry Out• Inspection Test Plan & Acceptance Criteria• Special Requirements
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LINING SYSTEM
1. Brick Lining
• Different Shapes
• Insulating & Dense Type
• Type of Mortar
2. Monolithic / Concrete Lining
3. Ceramic Fibre Lining( Blanket &
Module)
4. Combination
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FACTORS FOR LINING DESIGN & SELECTION OF MATERIALS
1. Operating Temperature
2. Mode Of Operation (Intermittent/ Cyclic, Continuous)
3. Furnace Atmosphere (Oxidizing, Reducing, Neutral)
4. Furnace Pressure ( +Ve, -Ve, Neutral)
5. Geometry Of Furnace
6. Type Of Furnace (Static, Rotating, Tilting)
7. Interface Temperature Between The Layers , Temp Gradient
8. Expected Casing Temperature And Heat Loss
88
MAJOR FACTORS CONSIDERED FOR LINING DESIGN
9. Requirement Of Furnace Efficiency
10. Physical Abuses Such As Abrasion, Erosion Etc.
11. Thermo-chemical Attack : Corrosion
12. Function Of Furnace: Heating Of Solid, Melting, Heating Of Gases, Hydrocarbons, Etc.
13. Gas Composition Within The Furnace (Sulfur, Sodium, Potassium, Chlorine, Hydrogen Etc.)
14. Expected Life Of Furnace
15. Cost And Economics
16. Ease Of Installation,
17. Future Ease Of Maintenance & Repair
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SELECTION OF REFRACTORIES
Chemical Composition
Apparent Porosity
Bulk Density
Co-efficient Of Thermal Expansion
Permanent Linear Change
Refractoriness Under Load
Pyrometric Cone Equivalent
10
SELECTION OF REFRACTORIES
Thermal Conductivity
Spalling Resistance
Performance Under Various Gaseous Atmosphere
Permeability
Mechanical Strength (Room Temperature & High Temperature)
Abrasion / Erosion Resistance
Resistance To Chemical Attack
11
HEAT FLOW CALCULATION
INPUT: Operating Temperature Ambient Temperature Operating Pressure External Wind Velocity Thermal Conductivity Emissivity Heat Flow Direction Inside Gas Composition
(Hydrogen, Etc.)
12
OUTPUT: External Shell Temperature Interface Temperature Heat Loss From Surface
THERMAL / HEAT FLOW CALCULATION
13
Layer 1: IFB, Gr. 28
Layer 2: IFB, Gr. 23
Layer 3: Fibre Block
1100°C
Layer 4: Fibre Block
800°C
Layer 1: MW Concrete
Layer 2: CRF Board
1260°C
Layer 3: Fibre Block
1000°C
Layer 4: Fibre Block
800°C
Layer 1: CRF
Modules 1430°C,
192kg/m³
Layer 2: CRF
Blanket 1260°C
Layer 1: CRF
Blankets
1430°C, 160kg/³
Layer 2: CRF
Blanket 1260°C
Heat Flow Calculation for: tAMB=27°C, tINS=1200°C, wind=0m/s, ε=0.95
tOUTS=72°C
qloss=576 W/m²
tOUTS=78°C
qloss=676 W/m²
Water Content≈92kg/m²
tOUTS=73°C
qloss=601 W/m²
tOUTS=69°C
qloss=528 W/m²
HOT
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LINING THICKNESS
Factors Determining Thickness : Operating Temperature
Corrosion, Erosion Etc.
Thermal Calculation
Design Casing Temperature
Strength
Installation Method
Service Life
14
LINING STRUCTURE AND SELECTION OF MATERIALS
SINGLE LAYER:
Low Operating Temperature Less Severe Conditions
MULTI LAYER: High Operating Temperature, Low Heat Loss Requirement Severe Conditions
COMBINED: Combination Of Brick, Block, castable,
Ceramic Fibre Material
1515
LINING FOR MOLTEN STEEL / SLAGLinings Consist Of A Safety Lining And A Working Lining
• Safety Lining Is Usually Provides Security & Insulation For The Vessel
• Working Lining Is In Direct Contact With Steel And Slag.
• Zone Wise Different Refractory To Match The Conditions It Is Exposed To Have Balanced Deterioration
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REFRACTORY WEAR MECHANISMS IN STEEL PLANT
– Corrosion• Chemical Reactions Between Slag Components (FeO, MnO
and SiO2) & Refractory
• Refractory Is Soluble In Steelmaking Slag
• Corrosion Can Be Minimized By Saturating Slag (With MgO From Dololime & Controlling Over Oxidation )
– Oxidation• Oxidation Occurs When Carbon In Refractory Reacts With
Oxygen From Slag (FeO) Or The Atmosphere And Burns
• As The Carbon Is Oxidized The Refractory Loses Its Strength
– Erosion• When Liquid Steel Or Slag Flows Over A Refractory Surface &
Abrades Surface
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HEIGHT OF LINING
Brick-wall
Mostly Self Supporting Type & Height Is Determined On Basis Of :
Stability Of Wall Load At Bottom Vertical Expansion Etc.
Monolithic Lining No Restriction In Height, As Weight Of Refractory Is Uniformly
Distributed Amongst The Anchors
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THERMAL EXPANSION OF LINING
• Expansion Joints In Brick Lining Are Necessary In Order To Protect The Lining And Shell Against Forces Due To Thermal Expansion Of Brick.
• Expansion Joints In Monolithic Lining Often Not Necessary Since Anchor Fitted To The Furnace Shell Allow Limited Movement Due To Thermal Expansion.
• Expansion Joints Are Necessary In Monolithic Lining That Are Not Supported By Anchor
• Size Of Expansion Joint Depends On Drying + Heating Shrinkage, Expansion Of Material , Shell / Casing Etc.
19
SHRINKAGE OF LINING :
Monolithic Refractory Lining Usually Shrinks During Post Installation Drying And When Cooled After Heating.
To Protect The Lining From Damage Due To Shrinkage, Joints Are Left At Appropriate Intervals So That These May Take Up The Shrinkage.
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ANCHORS FOR REFRACTORY LINING
Function Of Anchor:
To Hold Refractory in Position
Provide Support For Wall & Arches & Flat Roof
Prevent Bulging & Bowing Of Lining
Allow Horizontal & Vertical Movement Of Lining
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TYPES OF ANCHOR
• Metallic Anchors
• Ceramic Anchors
Metal Anchor
L Type
V Type
Y Type
Hexmesh
Chain Link Wire Mesh
Anchor For Ceramic Fibre Lining
Special Anchor
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DESIGN OF ANCHOR SYSTEM
Anchor Quality
Diameter Of Anchor Rod
Anchor Configuration
Anchor Spacing
Anchor Orientation
Anchor Height / Cover
Plastic Cap / Coating On Anchor
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SELECTION CRITERIA OF ANCHOR SYSTEM
Type Of Lining & Lining Thickness
Type Of Refractory Materials
Furnace Operating Conditions
Position Of Lining ( Vertical, Horizontal, Inclined, Floor, Circular Etc.)
Mechanical Movement Etc.
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CERAMIC ANCHOR
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STEEL FIBRE REINFORCEMENT IN REFRACTORY CASTABLE
ADVANTAGES:
• Higher Tensile, Flexural And Compressive Strength
• Improved Resistance To Damage From
Vibration, Impact And Thermal Shock
• Better Resistance To Cracking
• Better Performance Under Abrasive
Conditions
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TYPE OF STEEL FIBRES & THEIR CHARACTERISTICS :
• Type Of Fibre : Steel Wires, Thin
Steel Wares, Melt Extraction,
Shaving Thick Steel Plates
• Dia. Of Fibre (D) : 0.3 Mm To 0.5 Mm
• Length (L) : 25 Mm To 30 Mm
• Aspect Ratio (L/D) : 50 To 100
• Material Quality : SS 304, SS 410, SS 310 Etc.
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SULFURIC ACID CONDENSATION
S + O2 SO2 (Gas)
( Conversion ~ 1-5 %)
SO2 + O2 SO3 (Gas)
SO3 (Gas) + H2O (Steam) H2 SO4 (Gas)
Temp< Dew Point
120-160 0C
H2 SO4 (Liquid)28
Flue gas constituents: • H2O (Steam), SO2 & SO3 (Gases)• CO, CO2 , N2 , NOx , Cl, (Gases)• H2SO4 , HCl, HNO3 (Gases)
• Compounds of Na, V, Ash Etc.
(Depending of type of fuel, furnace charge, etc.)
PHYSICAL BARRIER INSIDE LINING
• Metallic Foil / Sheet ( SS, Al) Between Refractory Layers
• Thickness 0.1 to 0.15mm
Mainly For Cold Wall Design Furnaces:
• Casing Temperature Is Maintained Approx. 60 to 100 0C.
• Very High Thermal Efficiency Is Expected Heater,
Primary Reformer, Cracker
SS Sheet
TYPICAL SS SHEET BARRIER
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SS Foil Over Insulating Board
THANK YOU