Publish Time: 2026-06-21 Origin: 由AI辅助生成
In the design and renovation of high-temperature industrial kilns, the selection of lining materials will directly affect equipment life, energy consumption and production safety. Many engineering and technical personnel often hesitate between "mullite bricks" and "bead bricks" when selecting materials. Both materials seem to be able to withstand high temperatures, but their performance positioning and application scenarios are different. If you choose the wrong one, either the insulation effect will not be up to standard, or the life of the furnace lining will be greatly reduced.
As a professional comprehensive service provider of refractory materials in China, Shengyuan Refractories will explain to you the essential differences between these two materials today and provide you with a practical selection guide to help you avoid detours.
Mullite bricks refer to high-alumina refractory materials with mullite (3Al₂O₃·2SiO₂) as the main crystal phase. The alumina content is usually between 65% and 75%. It is a refractory product that can be customized in heavy or light weight. It is made of high-alumina clinker as the main raw material and is formed by high-pressure molding and high-temperature firing. It has high density and strength and is often used in the working layer or load-bearing structure of kilns.
Floating bead bricks are heat-insulating refractory products made of aluminum silicate glass hollow floating beads floated from fly ash in thermal power plants as the main raw material. The floating bead bricks are light, thin-walled and hollow. The floating bead bricks made by taking advantage of this feature have high porosity and low volume density. They are lightweight thermal insulation materials and are mainly used as the backing insulation layer of kilns. Direct contact with flames and material erosion are not recommended.
In the vernacular: Mullite bricks are "the main force in carrying heavy work", and bleached bead bricks are "the thermal insulation layer of a cotton-padded jacket".
1. Operating temperature and refractoriness
The refractoriness of mullite bricks can reach over 1790°C, and the load softening start temperature is as high as 1600~1700°C. It can withstand structural loads at high temperatures and is suitable for high-temperature load-bearing parts such as hot blast stove tops, blast furnace shafts, and ceramic sintering kilns.
The working temperature of floating bead bricks is limited by the temperature change of the reburning line, which usually cannot exceed 1150°C. The operating temperatures of floating bead bricks with different volume densities are different: PG-0.9 type is about 1150℃, PG-0.7 type is about 1100℃, and PG-0.5 type is about 1050℃. It is only suitable for medium and low temperature or backing insulation scenarios.
2. Strength and structural stability
The normal temperature compressive strength of mullite bricks can reach 70~260MPa, and it has good thermal shock resistance and corrosion resistance. It remains structurally stable under the combined action of mechanical stress and thermal stress.
The strength of floating bead bricks is much lower. The compressive strength of PG-0.9 type is only ≥5MPa, and the PG-0.5 type is even lower. Although the mechanical strength of floating bead bricks is relatively high among lightweight bricks, it is still not as good as mullite bricks and cannot withstand heavy loads and severe erosion.
3. Thermal insulation performance
This is the home of Piaozhu Brick. Due to the hollow beads and high closed porosity, the thermal conductivity of the bleached bead bricks is extremely low: the average thermal conductivity of the PG-0.9 type at 350°C is about 0.30 W/(m·K), and the PG-0.5 type is only about 0.20 W/(m·K). When used in cement rotary kilns, the surface temperature of the kiln body can be reduced by 100°C; when used in resistance furnaces, the energy saving can reach 30%.
Although mullite bricks also have lightweight thermal insulation series, their heavy series have relatively high thermal conductivity (above 1.2 W/(m·K)), and their thermal insulation performance is far inferior to that of floating bead bricks. Lightweight mullite bricks can provide thermal insulation to a certain extent, but the use temperature and safe use temperature are lower than heavy mullite bricks.
4. Chemical stability and corrosion resistance
Mullite bricks are high-aluminum materials and have good resistance to acidic and alkaline slags, and their low iron content (≤0.5%) further improves corrosion resistance.
Because the bleached beads are used as the main raw material, the chemical composition is close to that of clay. If there are too many pores, coal tar, carbon, etc. will easily penetrate into the pores and reduce the corrosion resistance. Therefore, floating bead bricks should not be in direct contact with highly corrosive media such as slag and molten metal.
5. Cost and construction convenience
Floated bead bricks have the advantages of wide sources of raw materials, relatively simple processes, and low production costs. At the same time, it is light in weight. The volume density of ordinary floating bead bricks is only 0.5~0.9g/cm³. It has a small load on the steel structure of the furnace body and is easy to construct and carry.
The production process of mullite bricks is more complex, especially the fused mullite bricks which require high-temperature sintering and are more expensive, but in exchange for longer service life and more applicable scenarios.
First of all: first look at the usage temperature. If the temperature of the working layer exceeds 1200°C and there are load-bearing requirements, then mullite bricks should be selected; for lightweight insulation parts with a backing insulation layer and a temperature below 1150°C, floating bead bricks are more cost-effective.
Article 2: Look at the contact medium. For parts that are in direct contact with slag, molten metal, and washed by high-speed airflow, choose mullite bricks; for clean hot air ducts, the inner wall of the kiln shell, and other parts that are not exposed to corrosive media, you can use floating bead bricks with confidence.
Article 3: Look at the comprehensive cost. Floated bead bricks have low one-time investment and good energy-saving effect. They are especially suitable for kilns with intermittent operation, and the comprehensive energy saving can reach 15% to 40%. Mullite bricks have a high single-time cost, but they have a long life and are maintenance-free, so they may not be more expensive in the long run.
In reality, many powerful design solutions use a composite structure of "mullite brick working layer + floating bead brick backing layer" - mullite bricks can withstand high temperatures and erosion, and floating bead bricks can lock in heat and reduce the temperature of the furnace wall. Each has its own strengths and the overall benefit is very good.
The relationship between mullite bricks and bleached bead bricks is not about "who replaces whom", but about each performing its own duties. Mullite bricks are the "hard bones" for load-bearing and corrosion resistance, while floating bead bricks are the "light cavalry" for thermal insulation and energy saving. Only by making an accurate match based on the actual working conditions of the kiln, temperature field distribution and economic budget can we achieve a win-win situation in terms of kiln life and energy consumption.
If you are choosing a lining material for your kiln, please follow our service number. Our technical engineers can also provide free material selection suggestions and furnace lining structure optimization plans based on your specific working conditions.