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Refractory Bricks for Tunnel Kilns in Clay Sintered Brick Plants

2025-10-16
Latest company news about Refractory Bricks for Tunnel Kilns in Clay Sintered Brick Plants

Refractory Bricks for Tunnel Kilns in Clay Sintered Brick Plants

Tunnel kilns are continuous high-temperature firing systems characterized by long structures and multiple thermal zones. Each section operates under different temperature, atmosphere, and mechanical stress conditions. Therefore, the proper selection and configuration of refractory bricks are critical for kiln performance, energy efficiency, and service life.

latest company news about Refractory Bricks for Tunnel Kilns in Clay Sintered Brick Plants  0


I. Types and Properties of Refractory Bricks Used in Tunnel Kilns

1. Main Types by Material

No. Refractory Type Major Composition Service Temperature (°C) Main Features Typical Applications
1 High Alumina Brick Al₂O₃ ≥ 55% 1300–1600 High compressive strength, good slag resistance, poor thermal shock resistance Firing zone roof, kiln door, flame-contact areas
2 Mullite Brick 3Al₂O₃·2SiO₂ 1350–1700 Low thermal expansion, excellent thermal shock resistance, no deformation Firing zone roof and wall, insulation zone
3 Cordierite Brick 2MgO·2Al₂O₃·5SiO₂ 1250–1400 Very low thermal expansion, excellent thermal shock resistance Lower firing zone, transition area
4 Lightweight High Alumina Brick Porous Al₂O₃ ≥ 50% ≤1350 Lightweight, excellent insulation Insulation layer, secondary wall, roof upper layer
5 Fire Clay Brick Al₂O₃ 30–45% 1200–1350 Economical, easy to construct, moderate thermal shock resistance Preheating zone, outer wall, flue lining
6 Insulating Brick SiO₂–Al₂O₃ ≤1100 Low thermal conductivity, lightweight Outer wall insulation layer
7 Silica Brick SiO₂ ≥ 95% 1650–1700 Excellent creep resistance at high temperature, acid-resistant Upper roof of firing zone, kiln head
8 Wear-Resistant Brick High-alumina or mullite-based composite ≤1400 Excellent abrasion and impact resistance Car wheel zone, track edge, kiln car top
9 Silicon Carbide Brick (SiC) SiC ≥ 70% 1500–1650 High thermal conductivity, oxidation and erosion resistance Burner zone, flame impact area, car base
10 Castable / Precast Block High alumina, mullite, or SiC-based 1300–1600 Good integrity and air-tightness Burner ports, arches, sealing joints
11 Ceramic Fiber Board / Blanket Al₂O₃ + SiO₂ ≤1400 Lightweight, excellent insulation, easy installation External insulation, kiln doors, wall lining
12 Shaped / Custom Brick Custom composition Varies Precision fit, customized geometry Burner brick, arch foot, transition pieces

 


II. Refractory Configuration and Construction Standards in Tunnel Kiln Design

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1. Recommended Material Configuration by Kiln Section

Kiln Section Recommended Brick Types Thickness (mm) Temperature (°C) Description
Roof (Firing Zone) Mullite / Cordierite + Lightweight High Alumina + Ceramic Fiber 500–550 1250–1300 Combines high strength and insulation
Wall (Firing Zone) High Alumina / Mullite + Lightweight Alumina + Fiber Board 500 1200–1300 Inner heat-resistant, outer insulating
Wall (Preheating Zone) Fire Clay + Lightweight Alumina 400–500 900–1100 Emphasizes thermal shock resistance
Insulation Zone Cordierite + Insulating Brick 400 900–1000 Reduces heat loss
Flue Lining Fire Clay / SiC Brick 250–350 800–1000 High erosion resistance
Kiln Door / Sealing Panels Mullite + Fiber Board + Steel Plate 450–500 1100–1200 Combines insulation and mechanical strength
Kiln Car Surface Cordierite / SiC / High Alumina Brick 230 1000–1250 Load-bearing and wear-resistant
Kiln Car Insulation Layer Insulating Brick + Ceramic Fiber 200–250 ≤900 Reduces heat conduction
Burner Port / Arch Foot SiC / Castable Blocks Custom 1300–1500 High thermal shock and erosion resistance

 


2. Construction and Masonry Standards

Item Technical Requirements
Brick Joints ≤ 2 mm; staggered joints ≥ 1/4 brick length
Anchoring Stainless steel anchors every 5 brick layers
Mortar Use matching refractory mortar (same base material)
Construction Sequence Build walls first, then arches; inner lining before outer layer
Drying & Heating-Up Initial heating rate ≤ 30°C/hour to prevent cracks
Arch Control Accurate curvature control to avoid stress concentration
Joints Sealing High-temp sealing compound or ceramic fiber filling

 


III. Standards for Qualified Refractory Materials

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1. Appearance and Dimensional Tolerance (per GB/T 2992.1, GB/T 16544)

Item Requirement
Surface Smooth, no cracks, chips, or dense pores
Dimensional Tolerance ±2 mm in length, width, and height
Density Uniformity ≤ ±0.05 g/cm³ variation within the same batch

 


2. Physical and Chemical Properties (Ref. GB/T 3995, GB/T 10325)

Property High Alumina Mullite Cordierite Fire Clay
Bulk Density (g/cm³) 2.3–2.6 2.4–2.7 1.9–2.2 2.0–2.2
Apparent Porosity (%) 18–22 15–20 25–30 22–26
Cold Crushing Strength (MPa) ≥60 ≥70 ≥45 ≥35
Permanent Linear Change (%) ±0.2 ±0.3 ±0.3 ±0.4
Refractoriness Under Load (°C) ≥1450 ≥1600 ≥1400 ≥1350
Thermal Shock Resistance (cycles 900°C–water) ≥20 ≥25 ≥30 ≥15

 


3. Inspection and Acceptance Procedure

Raw Material Inspection

Chemical composition (Al₂O₃, SiO₂, Fe₂O₃ content)

Phase analysis (XRD test)

Finished Product Testing

Dimensional and visual inspection

Fired bulk density and compressive strength test

Thermal shock resistance test

Documentation

Factory test report with chemical and physical data

Quality certificate compliant with GB/T, ISO, or ASTM standards

On-site Verification

Random sampling of ≥10% for re-test before use

Only approved materials may be used in kiln construction

 


IV. Selection Principles for Refractory Materials

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Principle Description
Temperature Matching Select materials according to thermal zones and service temperature
Thermal Shock Resistance Priority Roofs and burner zones require mullite or cordierite bricks
Mechanical Strength Coordination Use high alumina or SiC bricks for load-bearing areas
Insulation Coordination Combine dense inner bricks with lightweight outer layers
Supplier Qualification Must hold ISO/GB certification and third-party test reports
Sample Verification New suppliers must pass firing performance tests before approval

 


Conclusion

A well-designed refractory system ensures:

Stable tunnel kiln operation

Low energy consumption

Extended kiln service life

Consistent product quality

Proper selection and configuration of refractory bricks are fundamental to the success of modern clay sintered brick plants and to the overall efficiency of tunnel kiln construction projects.

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