Refractory Calcium Silicate Insulation Board — Up to 1100°C
Mingfa's refractory calcium silicate boards deliver reliable backup insulation for industrial furnaces operating at the highest temperatures. Three temperature grades — STD (1000°C), HT (1050°C), and EHD (1100°C) — with linear shrinkage below 2% at maximum rated temperature. Xonotlite-based, asbestos-free, ASTM C533 compliant.
1. Refractory Grade Overview
Not all high temperature calcium silicate board products are the same. Mingfa classifies its refractory-grade boards into three distinct temperature tiers, each formulated for a specific operating window. Selecting the correct grade prevents premature insulation degradation and ensures the designed thermal performance is maintained throughout the furnace campaign.
STD Grade
1000°C
LG-Standard HCS Series
The default choice for cement rotary kiln shell insulation, furnace wall backup, and ductwork where the insulation hot-face temperature stays below 900°C. Excellent thermal resistance at a competitive cost. Covers approximately 80% of industrial refractory calcium silicate applications.
HT Grade
1050°C
Intermediate High-Temperature
Bridges the gap between standard and extreme-duty grades. Specified when the calculated insulation hot-face temperature falls between 900°C and 980°C — common in cement preheater cyclones and steel reheat furnace walls with thinner refractory linings.
EHD Grade
1100°C
LG-High Temperature SCS Series
The flagship calcium silicate 1100°C product. Specified for the hottest zones: cement kiln burning zone, glass furnace crown, and calcining furnaces. Exceeds ASTM C533 Type II requirements at 927°C by a substantial margin. The same xonotlite chemistry as STD grade, with optimized crystal morphology for enhanced thermal stability.
2. Temperature Classification & Grade Selection
The table below matches furnace operating conditions to the recommended refractory calcium silicate grade. Always select a board rated at least 50-100°C above the calculated insulation hot-face temperature.
| Grade | Max Service Temp | Density (kg/m³) | Linear Shrinkage (12h at max temp) | Best For |
|---|---|---|---|---|
| STD (HCS-23) | 1000°C | 230 ±10% | ≤1.5% | Cement kiln shell (transition/safety zones), furnace backup walls, ductwork insulation |
| STD (HCS-25) | 1000°C | 250 ±10% | ≤1.5% | Heavy-duty kiln shell, petrochemical heater casing, power boiler insulation |
| HT (HCS-25HT) | 1050°C | 250 ±10% | ≤1.5% | Cement preheater cyclones, steel reheat furnace walls, thinner refractory linings |
| EHD (SCS-25) | 1100°C | 270 ±10% | ≤1.5% | Cement kiln burning zone, glass furnace crown/sidewall, calcining furnaces |
| EHD (SCS-27) | 1100°C | 270 ±10% | ≤1.5% | Extreme thermal environments, maximum safety margin applications |
Grade selection rule of thumb: The insulation hot-face temperature under the dense refractory working lining is typically 150-250°C below the furnace operating temperature, depending on refractory thickness and conductivity. For a furnace operating at 1400°C with 250mm of fireclay brick, the insulation hot-face is approximately 850-950°C — within the STD 1000°C rating. For a cement kiln burning zone at 1450°C with 200mm of magnesia-spinel brick, the insulation hot-face can reach 1000-1080°C — requiring EHD 1100°C grade. When in doubt, contact Mingfa for a thermal calculation.
3. Thermal Conductivity vs Temperature
Thermal conductivity increases with mean temperature for all calcium silicate products. The data below are measured by guarded hot plate method (ASTM C518) on production samples. Use these values for heat loss calculations and insulation thickness design.
| Mean Temperature (°C) | STD HCS-23 (W/m·K) | HT HCS-25HT (W/m·K) | EHD SCS-25 (W/m·K) |
|---|---|---|---|
| 200 | ≤0.068 | ≤0.070 | ≤0.072 |
| 400 | ≤0.088 | ≤0.092 | ≤0.095 |
| 600 | ≤0.108 | ≤0.114 | ≤0.118 |
| 800 | ≤0.128 | ≤0.136 | ≤0.141 |
The thermal conductivity follows an approximately linear relationship: λ = λ₀ + k · t, where λ₀ ≈ 0.056 W/m·K and k ≈ 0.00011 W/m·K² for STD grade. The HT and EHD grades have marginally higher conductivity due to their higher density — the trade-off for improved high-temperature stability. In practice, a 50mm EHD board provides approximately 92% of the thermal resistance of a 50mm STD board at the same mean temperature, which is negligible compared to the safety benefit of the higher temperature rating.
4. Shrinkage Data
Linear shrinkage is the most critical property for high temperature calcium silicate board performance. Excessive shrinkage opens gaps between insulation panels, creating heat leakage paths that degrade the thermal performance of the entire lining system. Mingfa boards are formulated to maintain dimensional stability at their rated service temperature.
Shrinkage Specification
All grades: linear shrinkage <2% after 12 hours exposure at the maximum rated service temperature (per ASTM C356). This means a 1000mm board shrinks by less than 20mm after sustained exposure to its rated temperature. In practice, because the insulation hot-face temperature is well below the furnace operating temperature, actual in-service shrinkage is typically below 1%.
Why 2% matters: Calcium silicate boards that exceed 2% linear shrinkage at their rated temperature experience joint opening, which reduces the effective thermal resistance of the insulation layer. A 5mm joint at every 600mm board edge represents a 0.8% open area — enough to increase heat flux by 10-15% at the joint locations.
Why Xonotlite Matters
Mingfa's low shrinkage is a direct result of the xonotlite (6CaO·6SiO&sub2;·H&sub2;O) crystal phase. Unlike tobermorite-based calcium silicate products that undergo phase transformation and significant shrinkage above 650°C, xonotlite undergoes a topotactic transformation to wollastonite only at 750-800°C — a gradual, low-shrinkage process that preserves the board's structural integrity through its rated temperature range.
Competing products that use tobermorite as the primary binder phase typically exhibit 3-5% shrinkage at their rated temperature, which can lead to early joint opening and reduced insulation effectiveness. This is why specifying calcium silicate 1100°C based on xonotlite chemistry is essential for high-temperature applications.
5. Cement Kiln Application Detail
The cement rotary kiln is the single largest application for refractory calcium silicate board. Each zone of the kiln has different temperature, mechanical, and chemical conditions that determine the appropriate insulation grade and thickness.
Preheater Cyclones
Temperature: Gas 800-1000°C; shell 120-180°C uninsulated.
Recommended: STD HCS-23, 50mm.
Cyclones have complex geometry with multiple access doors, expansion joints, and material inlet/outlet connections. Pre-cut boards with CNC-machined cutouts reduce installation time by 30-40% versus on-site cutting.
Burning Zone
Temperature: Clinker 1350-1450°C; shell 250-350°C uninsulated.
Recommended: EHD SCS-25, 50-75mm.Calcium silicate 1100°C grade is mandatory here. The insulation hot-face can reach 1000-1080°C behind magnesia-spinel brick. Shell temperature reduction of 50-80°C saves 3-5% of kiln fuel.
Tertiary Air Duct
Temperature: Air 800-1000°C; shell 130-180°C uninsulated.
Recommended: HT HCS-25HT or EHD SCS-25, 50mm.
The tertiary air duct carries combustion air from the cooler to the calciner. Insulating this large-diameter ductwork provides substantial energy savings because the duct surface area is significant (typically 80-150 m² for a 5000 t/d line).
Grate Cooler
Temperature: Clinker 200-1400°C at inlet; shell variable.
Recommended: STD HCS-23, 50mm (hot end); STD HCS-23, 25mm (cold end).
Cooler insulation focuses on the hot-end section where clinker enters at high temperature. The cold end typically does not require insulation and may need external cooling.
6. Glass Furnace Application Detail
Glass melting furnaces present unique challenges: sustained temperatures at the refractory hot face of 1570-1600°C, campaign lives of 8-15 years, and strict requirements for insulation-refractory chemical compatibility.
Crown Backup
Silica brick crown (300mm) is backed by 50mm EHD SCS-25 calcium silicate 1100°C board. The board is CNC-machined to match the crown arch radius and includes burner block cutouts per the furnace drawings. Typical crown shell temperature drops from 185°C to 95°C after insulation.
Sidewall Insulation
Behind AZS fused-cast or high-alumina refractory blocks, 50mm EHD SCS-25 board reduces heat loss through the melter sidewalls. Chemical compatibility is verified: calcium silicate does not react with AZS or alumina refractory at glass furnace operating temperatures.
Bottom Backup
Multi-layer bottom insulation: EHD SCS-25 (50mm) as the hot-face insulation layer beneath zircon paving, followed by standard calcium silicate board and insulating fire brick. The EHD layer carries the highest thermal load while maintaining dimensional stability.
7. Comparison: Mingfa Refractory Grades vs Industry Standard
How Mingfa's refractory calcium silicate boards compare against typical industry specifications for high-temperature calcium silicate insulation.
| Property | Mingfa EHD (1100°C) | Mingfa STD (1000°C) | ASTM C533 Type II | Industry Typical |
|---|---|---|---|---|
| Max Service Temperature | 1100°C | 1000°C | 927°C | 900-1050°C |
| Density (kg/m³) | 230-270 | 230-250 | ≤240 (Type I) / ≤320 (Type II) | 220-280 |
| Compressive Strength (MPa) | ≥2.5 | ≥2.0 | ≥1.7 | 1.5-3.0 |
| Thermal Cond. @ 200°C mean | ≤0.072 | ≤0.068 | ≤0.082 | 0.065-0.080 |
| Linear Shrinkage (at rated temp) | <2.0% at 1100°C | <2.0% at 1000°C | ≤2.5% at 927°C | 1.5-3.0% at rated temp |
| Crystal Phase | Xonotlite (verified) | Xonotlite (verified) | Not specified | Varies by manufacturer |
| Asbestos Content | Zero (XRD verified) | Zero (XRD verified) | Asbestos-free required | Asbestos-free |
| Manufacturing Standard | ISO 9001:2015 | ISO 9001:2015 | Not applicable | Varies |
Mingfa's EHD grade operates 173°C above the ASTM C533 Type II requirement of 927°C, while maintaining lower shrinkage and higher compressive strength. This performance margin is the result of xonotlite crystal phase optimization developed through three decades of continuous formulation refinement. For applications at or near the temperature limit of standard calcium silicate, EHD grade provides an engineered safety factor that protects against premature insulation degradation.