Design of Refractory Lining

DESIGN OF FURNACE & REFRACTORY LINING

By MK Maity (Materials & Corrosion Section, STC-J)

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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

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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

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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

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DESIGN & DETAIL ENGINEERING Refractory Materials: • • •

Material Specifications & Test Methods Quantity of Materials & Overages Suppliers

Installation: • • • • • •

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Installation Method Sequence of Installation Selection of Contractors Lining Dry Out Inspection Test Plan & Acceptance Criteria Special Requirements

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

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MAJOR FACTORS CONSIDERED FOR LINING DESIGN 9. 10. 11.

Requirement Of Furnace Efficiency Physical Abuses Such As Abrasion, Erosion Etc. 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.)

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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

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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

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HEAT FLOW CALCULATION

INPUT:        

Operating Temperature Ambient Temperature Operating Pressure External Wind Velocity Thermal Conductivity Emissivity Heat Flow Direction Inside Gas Composition (Hydrogen, Etc.)

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OUTPUT:

 External Shell Temperature  Interface Temperature  Heat Loss From Surface

THERMAL / HEAT FLOW CALCULATION

HOT

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

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tOUTS=73°C qloss=601 W/m²

tOUTS=69°C qloss=528 W/m²

LINING THICKNESS

Factors Determining Thickness :  Operating Temperature  Corrosion, Erosion Etc.  Thermal Calculation  Design Casing Temperature  Strength

 Installation Method  Service Life

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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

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LINING FOR MOLTEN STEEL / SLAG Linings 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 17

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.

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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 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.) S + O2

SO2 (Gas) ( Conversion ~ 1-5 %) SO2 + O2

SO3 (Gas) + H2O (Steam)

SO3 (Gas)

H2 SO4 (Gas)

Temp< Dew Point 120-160 0C 28

H2 SO4

(Liquid)

PHYSICAL BARRIER INSIDE LINING •

Metallic Foil / Sheet ( SS, Al) Between Refractory Layers

•

Thickness 0.1 to 0.15mm

SS Sheet

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

TYPICAL SS SHEET BARRIER

SS Foil Over Insulating Board

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THANK YOU