Lightweight silica bricks are also called silica insulation bricks. They are lightweight refractory materials with a silica content of more than 91% and a bulk density of less than 1.2g/cm3. The refractoriness and load softening temperature are similar to those of ordinary silica bricks with the same composition. They are made by using finely crushed silica as raw material, adding flammable substances to the ingredients or using gas generation method to form a porous structure, and then firing.
Lightweight silica bricks have low density, low thermal conductivity, high compressive strength and good durability. They are widely used in the glass kiln industry, mainly for the insulation of the kiln vault, thereby reducing heat loss and increasing the efficiency of the melting process. In the steelmaking industry, lightweight silica bricks are used for hot blast furnace walls and domes, high hot air channels, and high-temperature equipment such as blast furnace exhaust fans.
Lightweight silica bricks are also called silica insulation bricks. They are lightweight refractory materials with a silica content of more than 91% and a bulk density of less than 1.2g/cm3. The refractoriness and load softening temperature are similar to those of ordinary silica bricks with the same composition. Finely crushed silica is used as the raw material, and its critical particle size is usually no more than 1mm, and no less than 90% of the particles are smaller than 0.5mm. They are made by adding flammable substances to the ingredients or using a gas generation method to form a porous structure, and then firing.
Production process of lightweight silica bricks:
(1) Raw materials, mineralizers and binders for producing lightweight silica bricks
Quartz stone and silica bricks are used as raw materials, crushed by jaw crusher and then crushed into fine powder with particle size <0.088mm in drum mill for standby use.
Iron scale with Fe2O3+FeO content >95% and slaked lime are used as mineralizers; calcium lignin sulfonate solution is used as binder.
(2) Preparation of mud for producing lightweight silica bricks
Mud preparation: quartz powder, silica brick powder, lime milk, iron scale, bone glue, calcium lignin sulfonate solution, water. Put the prepared materials into a pebble ball mill and grind them for more than 10h-12h, then sieve to obtain mud. Put the ground mud into a beating drum, add alum, stir for 2min, then add the foaming agent, stir until there is no foam on the surface. The prepared foam mud should not be stored for a long time to prevent affecting its quality.
(3) Preparation of lightweight silica brick foaming agent
It is prepared by using sodium rosin acid foaming agent and stabilizer - glue solution.
Sodium rosin acid foaming agent is made by saponifying rosin with alkali.
Stabilizer - glue solution.
Add the prepared sodium rosin acid foaming agent to the stabilizer - glue solution, mix and stir to make the foaming agent.
When using the foaming agent, dilute it with 8 times hot water, put it in the foaming tube and foam for 15 minutes before use.
(4) Casting and drying of lightweight silica bricks
Place a bottomless wooden mold with a size of 285×150×100mm on the porous aluminum strip (or the ground), pad waste newspaper between the aluminum strip (or the ground) and the wooden mold, and then pour the foam slurry into the wooden mold. And make the surface convex to avoid the lightweight silica brick blank from sinking after drying.
The lightweight silica brick blank is dried in a tunnel dryer at a drying temperature of 30-45℃. After 24 hours of drying, it is demolded and turned over and laid on its side after 48 hours. After 96 hours, the moisture content of the lightweight silica brick blank is <3%, and it can be fired.
(5) Firing of lightweight silica bricks and finished product processing
Lightweight silica brick blanks are fired together with silica bricks in the tunnel kiln. The kiln is packed with racks and the brick blanks can be placed vertically. The firing system is the same as that of ordinary silica bricks, and the firing temperature is 1350-1375℃. The heat preservation is 32h, the total firing time is 196h, and the yield is 92.80%.
The fired brick blanks (or blanks) are cut and ground by a grinding machine and processed into products of various specifications and models. .
The physical and chemical indicators of lightweight silica bricks are as follows
|
Brand/project |
HXR-1.00 |
HXR-1.10 |
HXR-1.15 |
HXR-1.20 |
|
|
SiO2 % |
≥91 |
≥91 |
≥91 |
≥91 |
|
|
Bulk density g/cm3 |
≤1.00 |
≤1.10 |
≤1.15 |
≤1.2 |
|
|
Normal temperature compressive strength MPa |
≥2.0 |
≥3.0 |
≥5.0 |
≥5.0 |
|
|
Reburning line change rate % |
1550℃×2h |
≤0.5 |
≤0.5 |
||
|
1450℃×2h |
≤0.5 |
≤0.5 |
≥2700 |
||
|
0.1MPa Load softening start temperature℃ |
≥1400 |
≥1420 |
≥1500 |
≥1520 |
|
|
Thermal Conductivity W/(m.K) average temperature 350±10℃ |
≤0.55 |
≤0.60 |
≤0.65 |
≤0.70 |
|
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