Float glass furnace is one of the three important thermal equipment for glass production, which includes float glass melting furnace, float glass tin bath, float glass annealing furnace.
During glass production process, glass melting furnace plays the role of melting batch material into glass liquid and making it clarified, homogenized and cooled to the needed temperature for molding.
Tin bath is the key equipment for glass molding. Glass liquid with a temperature of 1050~1100℃ flows into tin bath liquid level from fluid passage. Glass liquid is flattened, polished on tin bath surface, then by mechanical drawing, ribbing and the control of edge roller, it forms glass belt with required width and thickness. At the process of moving forward, it gradually cools to 600℃ and leaves the tin bath.
The function of annealing furnace is to eliminate the residual stress and optical inhomogeneity of flat glass, as well as to stabilize glass internal structure. The continuous glass belt from tin bath, with 600℃ temperature, enters into annealing kiln through transition roller table.
All the three important thermal equipment need refractory material, the following 9 kinds of refractory material are usually used in glass kiln.
Glass Kiln Silica Brick
Silica brick is often used in glass kiln, its main composition is silicon dioxide(SiO2). Silica brick used in glass kiln should contain at least 94% of SiO2, the max. working temperature is 1600~1650℃, the density is 1.8~1.95g/cm3, apparent porosity is lower than 22%. The higher the porosity, the worse the quality of silica brick. The appearance of most silica brick is white crystal, the micro composition is the crystal of tridymite. Since silica brick can have crystal transformation at high temperature, and have volume expansion, especially at 180~270℃ and about 573℃, crystal transformation is severest, so during roasting kiln and cool repair of the kiln, some measures(such as loosening or tightening the braces) should be taken to adapt to silica brick crystal transformation.
The working temperature of silica brick is about 200℃ higher than fire clay brick, but it has poor corrosion resistance to glass liquid and alkaline floated material, therefore, it is used to mason main crown, breast wall, port and so on. During masonry, high silica refractory mortar, silica brick powder or materials with similar composition of silica brick are used as joint material.
Glass Kiln Fire clay Brick
The main composition of fireclay brick is Al2O3 and SiO2, Al2O3 content is about 30%~45%, SiO2 content is about 51~56%, density is about 1.7~2.4g/cm3, apparent porosity is about 12%~21%, the max. working temperature is 1350~1500℃. In glass industry, clay brick is used to mason the bottom of molten bath, sidewall of working part and channels, regenerator wall, crown, lower part checker bricks and flue. With the raising of temperature, the volume of clay brick also expands, but when temperature is over 1450℃, its volume shrinks again.
Glass Kiln High Alumina Brick
The main composition of high alumina brick is also SiO2 and Al2O3, but Al2O3 content is higher than 46%. The raw materials of high alumina bricks are corundum, high alumina bauxite or sillimanite(Al2O3-SiO2). The bulk density is 2.3~3.0g/cm3, apparent porosity is 18%~23%, max. working temperature is 1500~1650℃. The lower the porosity of high alumina brick, the better the corrosion resistance. High alumina bricks are mainly used to line cooling part bath the sidewall, regenerator crown, regenerator walls and so on.
Mullite Bricks
Mullite Brick is mainly composed of Al2O3, with about 75% content, as the primary mineral crystal is mullite, it is so called mullite brick. The bulk density is 2.7~3.2g/cm3, apparent porosity is 1~12%. The max. working temperature is 1500~1700℃. Sintered mullite bricks are mainly used for the masonry of regenerator walls.
Fused AZS Bricks
Fused AZS brick is also called white iron brick, generally, fused AZS bricks are divided into 3 classes(33%, 36%, 41%) according to zirconia content. Zirconia corundum bricks used in glass industry contain 50%~70% of Al2O3, 20%~40% of ZrO2, its bulk density is 3.4~4.0g/cm3, apparent porosity is 1%~10%, the max. working temperature is about 1700℃. Fused AZS bricks with 33% and 36% of ZrO2 are used to mason bath sidewalls, flame space breast wall, port fire nozzle, port jackarch, port stack, tongue arch and so on. Fused AZS bricks with 41% ZrO2 are used to line the corners of bath walls, throat and other parts where glass liquid scouring and corrosion are the severest. Fused zirconia corundum bricks are the most widely used fused refractory in glass industry.
Fused Alumina Brick
Fused alumina ricks mainly refers to α-βcorundum brick, fused βcorundum brick, they are mainly composed of corundum crystalline phase with 92%~94% of Al2O3, bulk density is 2.9~3.05g/cm3, apparent porosity is 1~10%, the max. working temperature is about 1700℃.
Fused alumina has excellent glass liquid permeation resistance, and almost has no pollution to glass liquid. Fused alumina bricks are widely used in working part bath sidewall, bath bottom, canal, working part charging channel bath sidewall, bottom and other parts where contact with glass liquid, but should not have pollution to glass liquid.
Quartz Brick
Quartz Bricks are mainly composed of SiO2, the content can reach to 99% or higher, its bulk density is 1.9~2.0g/cm3, refractoriness is about 1650℃, working temperature is about 1600℃. Quartz bricks have good acid corrosion resistance, they are mainly used for the masonry of acid boron glass bath sidewalls, flame space thermocouple hole bricks and so on.
Alkaline Refractory Brick
Alkaline Refractory mainly includes:
magnesia brick, alumina magnesia brick,
magnesia chrome brick, forsterite brick. Alkaline refractory bricks characterize in: good alkali corrosion resistance, high refractoriness(1900~2000℃). Alkaline bricks are usually used in glass furnace regenerator upper walls, regenerator arch, checkerwork, port and so on.
Glass Kiln Insulating Bricks
Glass kiln has large heat diffusion area, thermal efficiency is low, to save energy, large amount of heat insulating materials should be used to reduce heat loss. Especially for the bath sidewalls, bath bottom, arches, walls of regenerator, melter and working part, they also should have insulation to reduce heat diffusion. Heat insulation bricks have high porosity, low weight, the bulk density is lower than 1.3g/cm3. Since the thermal conductivity of air is poor, insulating bricks with large porosity will have good thermal insulation effect. The thermal conductivity coefficient of Insulating bricks is 2~3 times lower than ordinary refractory materials. So the higher the porosity, the better the insulation effect. Insulating bricks are classified into different categories, such as clay insulating bricks, silica insulating bricks, high alumina insulating bricks and so on.
