Description

Silica bricks are made of silica as the main raw material, and are heat-insulating fire-resistant products with a SiO2 content of not less than 91%. In addition to its heat-insulating and heat-preserving properties, silica heat-insulating refractory bricks largely maintain the characteristics of silica bricks, with a high load softening starting temperature. During the heating process, the volume expands slightly, which enhances the integrity of the kiln.

The manufacture of silica heat-insulating refractory bricks uses finely crushed silica as the raw material, and adds some waste silica bricks or waste silica heat-insulating refractory brick powder, mineralizers and burnout additives. According to a certain ratio, water is added to the mixer to mix into mud, which is formed mechanically or manually. The bricks can be loaded into the kiln only when the residual moisture is less than 0.5% after drying. In order to prevent the product from cracking due to the violent volume expansion caused by the polycrystalline transformation of SiO2, a relatively slow heating and cooling speed is required during firing.

The performance of QG-1.2 grade silicon insulating refractory bricks for industrial furnaces specified in the industry standard YB386-63 of the Ministry of Metallurgical Industry of China is as follows: the bulk density is not more than 1.2g/cm, the compressive strength at room temperature is not less than 3.43MPa, the temperature of the fire is not less than 1670℃, the softening temperature under load at 0.098MPa is not less than 1560℃, and the SiO2 content is not less than 91%.

Products Description

This silica brick product is suitable for masonry working temperature not exceeding 1550℃, not in direct contact with high-temperature molten materials and not directly exposed to corrosive gases, or for use as an insulation layer in industrial furnace linings.

Since silica dust is harmful to the human body, the process is more complicated than clay and high-alumina thermal insulation refractory bricks, and it accounts for a very small proportion of the total output of thermal insulation refractory materials.

The main crystal mineral composition of silica bricks at room temperature is a mixture of γ-tridymite, β-cristobalite and β-quartz, and the proportion varies depending on the process. The range is:

β-cristobalite 15%~60% γ-tridymite 35%~80% β-quartz 0%~10%

It is mainly used in coke ovens, blast furnace hot blast furnaces, and glass kilns. Some countries still use silica bricks for steelmaking electric furnace covers.

Silica bricks should be stored in a waterproof warehouse and can still be used after being slowly dried below 100℃ after being damp. The strength of water-containing silica bricks is affected by freezing and needs to be re-inspected. When building a furnace, expansion joints should be left according to the linear expansion rate provided by the manufacturer. The temperature-time heating curve for baking and periodic use should be reasonably formulated, especially in the stage before 600C when the expansion is more intense, which should be strictly controlled.

Brand/ltem		GZ-96	GZ-95	GZ-94	BG-96A	BG-96B	BG-95A	BG-95B
SiO₃ %		≥96	≥95	≥94	≥96	≥96	≥95	≥95
Fe₂0₃ %		≤1.0	≤1.2	≤1.4	≤0.8	≤1.0	≤1.2	≤1.2
Apparent Porosity %≤		≤22(24)			≤22(24)
Melting Index	＜20kg				≤0.5	-	≤0.7	-
	Unit weight≥20kg				≤0.5	-	≤0.7	-
Cold Crushing Strength MPa,≥	Unit weight＜20kg	35(30)			35(30)
	Unit weight≥20kg	30(25)			30(25)
Refractoriness Under Load KD ℃		≥1660	≥1650	≥1640 (Cemented silica1620)	≥1680	≥1670	≥1660	≥1650
True Density,g/cm³		≤2.34	≤2.35		≤2.34		≤2.35

Note: The values in brackets are indicators for manual forming

Lightweight silica bricks

The main raw material for manufacturing lightweight silica bricks is crystalline silica, the auxiliary raw material is silica sandstone, the mineralizer is burnt gypsum, and the binder is sulfite pulp waste liquid. The ingredients are as follows: crystalline silica 75~80%, silica sandstone 20~25%, burnt gypsum 5~7%, sulfite pulp waste liquid 1~2%. First, silica and silica sandstone are made into fine powder with a particle size of less than 0.088mm, mixed according to the above ingredients and added with 30~40% water. After grinding, the mud density is controlled to be 1.

7~1. 8g/cm³. Sodium rosinate foaming agent is prepared with rosin and alkali, and the ratio is rosin: water: NaOH=10:10:1. After the three are mixed and heated, they are added into the glue solution. The glue ratio is glue: water=22:78. Before using the foaming agent, dilute the foaming agent with 4 to 5 times hot water. And foam for 10 to 15 minutes.

Put the silica slurry and foaming agent in the beating barrel to prepare the foam slurry. In order to improve the strength of the semi-finished lightweight silica bricks, 1% bone glue and 0.5% alum can be added. The lightweight silica bricks are formed on the drying car. Spread newspapers on the aluminum plate of the drying car, inject the slurry into the mold, and then use a small hammer to knock the mold frame to make the foam slurry vibrate, so that the structure of the lightweight silica brick body is uniform. Push the drying car carrying the body into the tunnel dryer for drying.

The inlet temperature of the dryer is 100~120°C, the outlet temperature is 50~60℃, the drying time is 20~24h, and the residual moisture of the body after drying is less than 0.8%. The firing of lightweight silica bricks is carried out in a downdraft kiln, the firing temperature is 1360~1370℃, and the heat preservation is 40~48h. The products out of the kiln are cut and ground into finished lightweight silica bricks. By controlling the density of the slurry, various lightweight silica brick products with a volume density of 0.4g/cm3 to 1.2g/cm3 can be manufactured.

Brand/ltem		HX-GQ-1.00	HX-GQ-1.10	HX-GQ-1.15	HX-GQ-1.20
SiO₂ %		≥91	≥91	≥91	≥91
Bulk Density g/cm³		≤1.00	≤1.10	≤1.15	≤1.2
Cold Crushing Strength MPa		≥2.0	≥3.0	≥5.0	≥5.0
Permanent Linear Change %	1550℃ x2h			≤0.5	≤0.5
Permanent Linear Change %	1450℃ x 2h	≤0.5	≤0.5		≥2700
0.1MPa Refractoriness Under Load ℃		≥1400	≥1420	≥1500	≥1520
Thermal Conductivity W/(m.K) Average temperature 350±10℃		≤0.55	≤0.60	≤0.65	≤0.70

Hot Tags: lightweight silica brick, China lightweight silica brick manufacturers, suppliers, factory, Sintered Mullite Bricks, Refractory Materials for Glass Kiln

Lightweight Silica Brick

Products Description