Material Selection and Configuration for Refractory Materials in Glass Furnaces

Key Details in the Refractory Material Configuration for Glass Furnaces (categorized into five major types: material selection, masonry construction, layered structure, operational condition adaptation, and production & maintenance; electrically fused bricks) /  Silica brick /  Key points on magnesia refractories)

I. Material Selection and Compatibility Details (The Easiest Pitfalls)

1.  The liquid level line area is of paramount importance.

Large temperature difference between the liquid surface and the bulk, alkali vapor +  Bidirectional erosion of the glass melt; the use of ordinary materials alone is strictly prohibited. AZS33 , must be upgraded AZS36/41 Shrinkage-free electrofused brick;

Silica bricks must not come into contact with the glass melt surface; when exposed to liquid soda–lime glass, they rapidly dissolve and form silica scale.

The height of the liquid‑level line bricks should be provided with an adequate margin; during masonry, the liquid‑level line must fall at the center of a whole brick and must not align with a mortar joint.

2.  Air-assisted combustion kiln /  Differences in refractory materials for all-oxygen kilns

Conventional cross‑flame and horseshoe‑flame air kilns: silica bricks can be used in the flame space vault and the upper portion of the sidewalls, resulting in low costs.

Oxy-fuel kiln: The flue gas contains an extremely high water vapor content, making silica bricks highly susceptible to pulverization and spalling; the entire flame zone is replaced by α. - β-alumina / Electrofusion AZS , silicon bricks cannot be used;

In all‑oxygen kilns, ordinary magnesia bricks must not be placed near the flame zone, as water vapor will react with the bricks and cause them to disintegrate.

3.  Selection of refractory materials under glass‑product category constraints

Colorless float glass / Daily-use white glass: Chromium‑containing, high‑iron refractories (magnesium‑chromium bricks, ordinary chrome corundum) are prohibited, as they can cause black spots, bubbles, and color streaks; the liquid surface and flow channels must be low in iron. AZS , chromium-free corundum;

Tinted glass (green glass) /  Brown glass: The regenerator can use magnesia-chrome bricks, but the melting tank still cannot use chromium-based materials.

Borosilicate glass: Boron vapor is highly corrosive to silica bricks and ordinary materials. AZS , switch to high-zirconia fused cast bricks and sintered zirconia‑alumina;

Lead glass: Lead vapor corrodes magnesia bricks; therefore, the heat‑storage top layer does not use magnesia bricks but instead employs high‑alumina zirconia–mullite refractories.

4.  Details of Layered Material Selection for the Heat Storage Chamber

Top-level high-temperature zone ( 1300 (above ℃): High-purity directly bonded magnesia bricks must be used; ordinary magnesia bricks have an insufficient load‑softening temperature and are prone to collapse.

Middle management 1000~1300 ℃: Do not use single‑phase magnesia–chromia bricks; under high‑alkali fly‑ash operating conditions, prioritize magnesia–alumina spinel bricks to avoid hexavalent chromium environmental concerns.

800~1000 Temperature zone: Magnesium-based materials are prone to cracking due to the magnesia–calcia reaction; they transition to high-alumina bricks, and magnesium bricks cannot be directly abutted against clay bricks.

Bottom low-temperature zone: Use low-porosity, dense clay bricks to prevent alkali dust penetration and pulverization.

5.  Avoid direct contact between refractories of different materials (to prevent reaction‑induced cracking).

Silica brick ↔   Magnesia bricks: At high temperatures, silicon and magnesium undergo a chemical reaction to form low-melting-point compounds, causing the joints to melt through rapidly; therefore, high-alumina isolation bricks must be inserted in the middle as a transition layer.

AZS Electrofused brick ↔ Silica bricks: A zircon–mullite transition layer is provided at the joint.

Magnesia brick ↔ High-alumina bricks: exhibit no reaction at medium and low temperatures, but require a thin isolation layer for long-term use at high temperatures.

II. Details of the Composite Lining’s Layered Structure (Common to Pool Bottom, Breastwall, and Vault)

All high-temperature areas must have a working layer. +  Transition layer +  The insulation layer has a three-layer structure; it must not be made of a single thick brick.

Standard stratification of the molten pool bottom (from top to bottom)

Electrofusion AZS Working layer ( 150~250mm ) → Sintered zirconia–mullite transition layer ( 100mm ) → Heavy-duty high-alumina brick → Lightweight high-alumina insulating brick → Aluminosilicate fiber board;

Details: It is strictly prohibited to apply insulation fibers directly to electrofused bricks; high‑temperature shrinkage of the fibers may cause the bricks to become detached and crack.

Layered arrangement of the parapet wall and the front face wall: AZS Working layer +  Zircon–mullite transition brick, with external insulation;

Refractory insulation for the arch: Thick fiber insulation cannot be laid directly on the upper portion of the silica brick arch; instead, a layer of lightweight silica bricks should be used as a transition to prevent uneven thermal expansion and subsequent spalling.

Layered staggered joints: The mortar joints of each brick course must be offset vertically; continuous vertical joints can create pathways for penetration, allowing molten glass and flue gases to erode the inner insulation layer along these gaps.

III. Supporting Details for Masonry Construction (Directly Affecting Kiln Life)

1.  Electrofusion AZS Special requirements for bricks

Distinguishing the pouring port (shrinkage cavity surface): The side with the shrinkage cavity must face outward (the fire‑back side), while the smooth, dense surface should be oriented toward the molten glass. / Flame; if the shrinkage cavity faces inward, it will rapidly absorb glass and cause blistering and cracking.

Masonry joints: Dry-laid in the glass melt contact zone, with joint width ≤ 0.5mm , thick slurry is prohibited; the upper flame zone can be equipped with a dedicated accessory. AZS Fire clay;

The cut surface of electrofused bricks must not face the molten glass; such surfaces are highly porous and exhibit poor corrosion resistance. During installation, the entire smooth side should be positioned toward the corrosive environment.

2.  Key Points for Laying Silica Bricks

Silica bricks must be bonded with silica refractory mortar; the use of high-alumina or magnesia mortars is strictly prohibited, as they can cause cracking due to high-temperature melting when used with dissimilar mortars.

Expansion joints shall be provided: silica bricks exhibit significant thermal expansion, each… 1.5~2m Settings 20~30mm Expansion joints shall be filled with refractory fiber; failure to provide such joints may result in arching and collapse of the vault.

After wet masonry, the kiln must be thoroughly dried, with a gradual temperature rise, to prevent the moisture in the refractory mortar from vaporizing and causing the silica bricks to crack or spall.

3.  Unified Specification for Expansion Joints

Different materials have different coefficients of thermal expansion; expansion joints shall be provided separately and must not be shared.

No continuous expansion joints are provided in critical erosion zones such as the liquid‑surface line and the molten‑glass drainage cavity, to prevent molten glass from penetrating.

The checker bricks in the heat storage chamber are provided with vertical and horizontal expansion joints; at high temperatures, thermal expansion and compression can cause the checkerwork to collapse.

4.  Key to preventing seepage in brick joints

Areas in contact with the molten glass: vertical and horizontal joints should be kept as short as possible to minimize pathways for liquid penetration.

The bottom bricks are laid in a herringbone pattern with staggered joints to eliminate continuous vertical mortar joints.

Flow‑through cavities and small, irregularly shaped bricks for the riser passages are paired with specially designed prefabricated composite bricks to minimize joint gaps.

IV. Details of Adaptation to Temperature and Thermal Shock Conditions

Areas subject to frequent thermal cycling (charging ports, observation ports, and service doors): prohibit the use of pure silica bricks and ordinary magnesia bricks; instead, select high‑thermal‑shock‑resistant zirconia‑mullite or α‑alumina bricks. - β-alumina;

Bubble bricks and the periphery of the stirrer: subjected to intense scouring by the molten glass; select high-density materials. AZS41 Electrofused bricks, enhancing resistance to erosion;

Local overheating location (small furnace flame outlet): conventional brick thickening. 20%~50% , or a double-layer composite refractory material;

Low-temperature dew-point zone (at the flue gas outlet and chimney): Alkaline condensation and penetration occur in the flue gases; therefore, dense, low-porosity clay bricks are selected, with a thickened inner lining.

V. Details on Protection Against Erosion by Alkali Vapors, Molten Materials, and Glass Melt

Severe material spillage from the feed opening; the lower portion of the front wall has been thickened. AZS , with a zirconia–mullite protective layer on the upper section, accumulated slag can accelerate the erosion and melting of the refractory material;

Within the kiln, sodium and potassium alkali vapors accumulate upward, and the erosion rate at the lower part of the arch and along the top of the sidewalls is comparable to that of the kiln wall. 2  times, the refractory thickness at this location has increased. 30%；

Alkali dust condensation in the heat‑storage chamber is the primary cause of refractory brick damage: the surface of the top‑layer magnesia bricks can be coated with a high‑temperature protective layer to reduce alkali penetration.

It is strictly prohibited to expose lightweight insulating bricks directly to the flame zone, as alkali vapors can rapidly penetrate these bricks, leading to extensive spalling.

VI. Details for Kiln Drying and Temperature Ramp-Up (Design should be planned in advance during the configuration phase)

When selecting refractory materials, allow for expansion allowances during kiln firing; different refractories exhibit significantly varying heating rates (e.g., silica bricks). 5-10 °C /h Within, AZS Can 10~15 °C /h );

Electrofusion AZS The brick contains a small amount of glassy phase; during the heating-up stage. 600~900 ℃ Slow down the heating rate to prevent thermal stress-induced cracking;

Prior to the commissioning of the new kiln, a corrosion allowance was provided in the refractory lining of the liquid‑level zone, with the designed brick thickness exceeding the theoretical wear thickness. 100mm , extend kiln life;

VII. Details on the Trade-off Between Cost and Lifespan

Do not blindly use high-end electrofused bricks throughout the entire kiln; for low-temperature flues and the heat‑storage bottom layer, use clay bricks. /  High-alumina bricks are used to control costs; critical erosion points such as the molten‑metal surface, flow‑through holes, bubbling bricks, kiln‑ledge bricks, charging ports, and small furnace openings are never compromised in terms of material quality.

Do not simply reduce the refractory thickness to cut costs: thinning the liquid‑level line and the tuyere. 20mm , the kiln age is directly shortened One third ；

Environmental Pre‑emptive Measures: For new kilns, prioritize chromium‑free refractories (using magnesium–aluminum spinel to replace magnesia–chromia bricks) to avoid the costs associated with treating chromium‑containing solid waste.

VIII. Often Overlooked Hidden Details

An insulation layer must be provided between the steel structure and the refractory lining to prevent high‑temperature deformation of the steel plate from compressing the refractory material.

The steel structure at the kiln bottom is provided with heat‑dissipation channels, and the insulation layer on the kiln floor is not fully sealed to prevent excessive heat buildup and overheating at the base.

Special-shaped bricks (including flow‑through holes, bubble bricks, and small furnace arch bricks) shall all be sourced from the same manufacturer to ensure compatibility of refractory materials and consistent thermal expansion coefficients, thereby preventing joint cracking.

Maintenance provisions: For wear‑prone components (such as the small furnace and refractory bricks lining the hearth), modular precast bricks are used, allowing individual replacement during subsequent cold repairs without requiring large‑scale dismantling of the kiln.