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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

22

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

6

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

7

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

99

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

13

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

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

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