Calcium Silicate Glass Furnace Insulation — Crown, Sidewall & Bottom Backup
Mingfa's calcium silicate glass furnace insulation products are engineered for the most demanding thermal environment in industry: the glass melting furnace at 1570-1600°C. MFBL composite bricks and LG-High Temp 1100°C boards provide backup insulation for crown, sidewall, bottom, and regenerator target walls — reducing shell temperature, fuel consumption, and refractory thermal stress.
1. Glass Industry Thermal Insulation Overview
Glass melting furnaces operate at the highest sustained temperatures of any continuous industrial process. The melter zone hot face reaches 1570-1600°C — temperatures at which silica sand, soda ash, and limestone fuse into molten glass. The refiner and working end operate at 1300-1400°C, where the glass homogenizes and cools to forming viscosity. These extreme temperatures place severe demands on every layer of the furnace lining, from the hot-face refractory to the outermost insulation.
Crown
The arched roof spanning the melter. Constructed of silica brick (300mm typical), the crown is exposed to flame and combustion gases at 1600°C. Backup insulation behind the silica brick reduces heat loss and the thermal gradient across the brick, which extends refractory life by reducing thermal expansion stress cycling. Crown insulation must be CNC-machined to match the arch radius and include burner block cutouts.
Sidewall
The vertical walls of the melter, typically AZS (alumina-zirconia-silica) fused-cast blocks. The sidewall must resist corrosion from molten glass at the melt line while withstanding the hydrostatic pressure of the glass bath. Backup insulation behind the AZS blocks reduces heat loss through the sidewall while maintaining chemical compatibility — calcium silicate does not react with AZS at furnace operating temperatures.
Bottom
The furnace floor carries the weight of the entire glass bath (specific gravity ~2.5) plus the refractory paving. A multi-layer bottom insulation system distributes the thermal and mechanical loads: zircon paving at the hot face, high-density MFBL brick for load support, calcium silicate board for thermal resistance, and insulating fire brick at the cool face.
Regenerator
Regenerative chambers preheat combustion air to 1100-1300°C by cycling between heating (exhaust gas) and cooling (combustion air) phases. Target walls in the regenerator are exposed to thermal cycling, alkali vapor condensation, and particulate carryover. Calcium silicate backup insulation behind the regenerator refractory checkerwork reduces heat loss and improves thermal efficiency.
2. MFBL Series for Glass Furnaces
The MFBL series is Mingfa's purpose-designed glass industry insulation board and brick range for glass furnace backup insulation. Five density grades allow specifiers to balance thermal resistance and mechanical strength for each furnace zone.
MFBL-30Q (300 kg/m³)
Compressive ≥3.0 MPa. For crown backup where mechanical load is minimal — primarily self-weight of the insulation. Maximum thermal resistance in the MFBL series. Thermal conductivity 0.08 W/m·K at 100°C mean. Rated 1000°C.
MFBL-50 & MFBL-60 (500-600 kg/m³)
Compressive ≥5.0-6.0 MPa. The versatile mid-range: sidewall backup behind AZS blocks, general furnace backup, and bottom paving support in moderate-load areas. Thermal conductivity 0.10-0.12 W/m·K at 100°C mean.
MFBL-70 & MFBL-85 (700-850 kg/m³)
Compressive ≥8.0-10.0 MPa. For bottom paving support where the brick carries the weight of zircon paving, glass contact refractories, and the glass bath. Also suitable for regenerator target walls subject to mechanical impact. Higher thermal conductivity (0.16-0.20 W/m·K) is the trade-off.
3. Product Specifications
Complete technical data for calcium silicate glass furnace insulation products. Both board (LG-High Temp) and brick (MFBL series) grades are included.
| Grade | Form | Density (kg/m³) | Compressive (MPa) | Thermal Cond. @ 100°C (W/m·K) | Max Temp (°C) | Typical Application |
|---|---|---|---|---|---|---|
| LG-High Temp SCS-25 | Board | 270 ±10% | ≥2.5 | ≤0.072 | 1100 | Crown backup, sidewall insulation |
| MFBL-30Q | Brick | 300 | ≥3.0 | ≤0.08 | 1000 | Crown backup (low load) |
| MFBL-50 | Brick | 500 | ≥5.0 | ≤0.10 | 1000 | Sidewall backup |
| MFBL-60 | Brick | 600 | ≥6.0 | ≤0.12 | 1000 | General backup, bottom paving |
| MFBL-70 | Brick | 700 | ≥8.0 | ≤0.16 | 1000 | Bottom paving, maintenance areas |
| MFBL-85 | Brick | 850 | ≥10.0 | ≤0.20 | 1000 | Bottom paving support (high load) |
All products are xonotlite-based, asbestos-free, and compliant with ASTM C533. Linear shrinkage ≤1.5% after 24 hours at rated temperature (ASTM C356). Standard board dimensions: 600 × 1000mm, 600 × 1200mm. Standard brick: 230 × 114 × 65mm. Thicknesses from 25mm to 100mm in 5mm increments; custom sizes available.
4. Application: Crown Backup, Sidewall Insulation, Bottom Paving & Regenerator Target Walls
Typical lining configurations for each glass furnace zone, with the roles of calcium silicate glass furnace insulation products clearly defined.
Crown Backup
From hot face outward: Silica brick (300mm) + MFBL-30Q brick (50mm) + LG-High Temp board (50mm). The silica brick handles the 1600°C hot face. The MFBL-30Q provides moderate thermal resistance with structural competence. The outer board provides maximum thermal resistance. Composite U-value: approximately 0.6 W/m²·K vs 1.8 W/m²·K for uninsulated silica brick alone.
Sidewall Insulation
From hot face outward: AZS fused-cast block (200mm) + MFBL-50 brick (50mm). Optional additional 25-50mm LG-High Temp board outside the brick for higher thermal resistance. The AZS block provides corrosion resistance against molten glass. The MFBL-50 supplies insulation and mechanical support for the tall sidewall refractory column.
Bottom Paving
From hot face outward: Zircon paving (100mm) + MFBL-85 brick (75mm) + LG-High Temp board (50mm) + insulating fire brick (65mm). The multi-layer design prevents excessive heat loss into the furnace substructure. MFBL-85 directly supports the zircon paving under the full weight of the glass bath (density ~2.5 g/cm³).
Regenerator Target Walls
LG-High Temp board or MFBL-50 brick installed behind the regenerator refractory checkerwork. Target walls are exposed to thermal cycling between 600°C and 1300°C, alkali vapor condensation (sodium sulfate), and particulate carryover. The backup insulation reduces thermal cycling amplitude in the refractory, extending regenerator life between repairs.
5. Installation Methods for Glass Furnaces
Glass furnace insulation installation follows strict procedures because the insulation cannot be accessed or repaired during the 8-15 year campaign life. Quality of installation directly determines long-term insulation performance.
CNC Precision Pre-Cut Boards
Crown boards are CNC-machined to match the furnace crown arch radius and include burner block cutouts, thermocouple penetrations, and doghouse openings per the furnace engineering drawings. Pre-cut boards eliminate field cutting, reduce installation time by 3-5 days for a typical furnace rebuild, and ensure consistent joint quality.
Numbered installation sets: Crown boards are numbered for installation sequence, matching the construction drawing. This is particularly valuable for the complex geometry at the crown-to-sidewall transition and around the doghouse.
Brick Laying & Board Fixing
MFBL bricks are laid in running bond pattern with 1-2mm mortar joints using high-temperature inorganic silicate mortar. For bottom paving, bricks are laid on a level bed to provide uniform support for the zircon paving layer above.
LG-High Temp boards are fixed with stainless steel studs (304 or 310 SS, M8 or M10) welded to the steel shell. Stud grid: 400 × 300mm for 50mm board, 500 × 400mm for 75-100mm board. Joints in multi-layer installations are staggered by at least 100mm to prevent direct heat leakage paths.
6. Case Reference: Egypt Float Glass Furnace & Linyi Glass Production Line
Field-verified performance of Mingfa calcium silicate glass furnace insulation in commercial glass production.
Egypt Float Glass Furnace (2019)
Project: Cold repair of 600 tonnes-per-day float glass line, Suez region.
Supply: 2,800 m² LG-High Temp board (50mm crown), 1,400 m² MFBL-30Q brick (50mm crown backup), 600 m² MFBL-50 brick (sidewall), 400 m² MFBL-85 brick (bottom paving).
Results: Crown shell temperature reduced from 185°C to 95°C. Natural gas consumption reduced from 178 Nm³/tonne glass to 164 Nm³/tonne — 8% saving. After 5 years operation, shell temperature modestly rose to 102°C. No crown refractory hot repair patches required (previous campaign needed patches at years 5 and 7).
Linyi Container Glass Line (2021)
Project: New construction of 350 tonnes-per-day container glass furnace, Linyi, Shandong Province.
Supply: Complete insulation package including LG-High Temp board for crown and upper sidewall, MFBL bricks for sidewall and bottom backup.
Results: Shell temperature at design targets from commissioning. Furnace operating at 4.5% lower specific energy consumption compared to sister line without calcium silicate backup insulation. No insulation-related issues after 24 months of continuous operation. The proximity of the Linyi site to Mingfa's Laizhou factory (approximately 3 hours by road) enabled direct technical support during installation.
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