The Use Of Silica Brick In The Glass Furnace

Since the silica brick has low price, high purity, high softening temperature under load, no pollution to glass liquid and good resistance to R2O gases and aicd gases, it is widely used in the crown of the glass furnace, the upper part of the suspended wall, the back wall and the front wall.

The SiO2 content in the silica brick used in the glass furnaces should be controlled. And it should be mainly composed of cristobalite. For large glass furnaces and oxy-fuel glass furnaces, refractory materials with high purity, good creep resistance and good corrosion resistance are used.

Since the advent of brick, there are three types of brick. The first is the common silica brick. the second is high quality silica brick. the third category is improved high quality silica brick.

With the development of glass mleting technology, silica bricks with better performance are required.

The Checker Work of Glass Furnaces

The checker work of glass furnaces is subjected to more serious corrosion than the crown and sidewall since all checker bricks are subjected to high temperature, duct and alkali vapor. The plugging and collapsing are the main reasons for the shutdown and cold repair of glass furnaces. Therefore, the refractory materials of the checker work should have high mechanical strength, low creep and good resistance to the changes in temperature and atmosphere and alkali corrosion and does not adsorb dust.

In the top part of the checker work, the temperature is high, which can reach up to 1400-1500℃. It is subjected to the most severe erosion by alkali vapor and dust. Rebonded fused magnesia brick is used here. Since rebonded fused magnesia brick contains less silicate phase, periclase crystals are fully developed and are directly bonded, which delays and deters the growing speed of the periclase crystals under the effect of alkali vapor and cracking and pulverizing of bricks.

In the upper part of the checker work, the temperature is 1100-1400℃. Rebonded magnesia brick 95 is used.

In the middle part of the checker work, the temperature is 800-1100℃, within which alkali metal sulfate is condensed and magnesium and calcium checker work severely eroded by Na2O and SO3. It is accompanied with large expansion of bricks and badly damaged. Therefore, the site should not use magnesia brick but direct bonded magnesia chrome brick, magnesia zirconia brick, synthetic magnesia olivine brick and magnesia alumina spinel brick.

In the lower part of the checker work, the temperature is low here and the corrosion is not quite severe. However, it is close to the flue and directly affected by cold air, so it should have good thermal shock resistance and low prices. low porosity fire clay brick is used here.

Applications of fire clay bricks

Fire clay brick plays a versatile role in the many industries.
Fire clay brick can be used in the metallurgical industry. Fire clay materials including shaped refractory materials and unshaped refractory materials acount for about 70% of the total refractory materials. Hard clay is used to produce refractory materials for theblast frunace, hot stove, ladle lining brick and plug brick.
High-alumina clay is used to produce alumina bricks for electric furnaces and blast furnaces, high aluminum lining brick and high alumina refractory mud. Hard clay and high alumina clay are often calcined into clinker at high temperature (1400 - 1800℃).
Refractory clay also has important roles in the grinding industry, chemical industry and ceramics industry. High-alumina clay can be made into abrasive materials by melting in an electric arc furnace. Fused corundum abrasive material is currently the most widely used an abrasive material. It acounts for 2/3 of the total abrasive materials.
High alumina clay can be used to produce a variety of aluminum compounds such as aluminum sulfate, aluminum hydroxide, aluminum chloride, aluminum potassium sulfate and other chemical products. In the ceramic industry, hard clay and semi-hard clay can be used to manufacture household porcelain, construction porcelain and industrial porcelain.
In the construction materials industry, refractory clay can be used to produce high alumina bricks, phosphate high alumina refractory bricks and high alumina fused cast bricks. High-alumina clay can be made into aluminum-containing cement by calcining and then mixing with limestone. This quick-setting cement has strogn heat and corrosion resistance.

The Composition and Properties of Magnesia Brick

Magnesia brick is a basic refractory product with periclase as its main mineral phase. It contains not less than 91% MgO and not less than 3.0% CaO.
Magnesia brick is composed of 80-90% periclase and 8%-20% other mineral phase including magnesium ferrite (MgO·Fe2O3), forsterite (2MgO · SiO2) and Calcium and magnesium olive stone (CaO·MgO·SiO2).Silicate glass contains about 3-5% magnesium, calcium and iron. These silicates may contain tricalcium silicate (3CaO · SiO2), magnesium rhodonite (3CaO · MgO · 2SiO2), calcium and magnesium olivine and forsterite, dicalcium silicate (2CaO · SiO2).
Magnesia brick has good thermal conductivity, good thermal expansion, good corrosion resistance to alkali molten slags and bad corrosion resistance to acid molten slags. Due to the low-melting silicate cements surrounded periclase, the beginning point of the softening temperature under load is not too high, but the collapse temperature is close to the beginning point. Its refractoriness is over 2000℃, but it does not make sense in the actual use. Bad thermal shock stability is one of the main reasons for the destruction.
In the storage and transport, special attention should be paid to moisture-proof to avoid burst after affected with damp.

The Application of Dense Zircon Brick in Glass Furnaces

Zircon is chemically inert with good erosion resistance to high temperature molten glass and slag solution. High dense zircon brick made of zircon powder as the main raw material has good high temperature strength and strong resistance to glass liquid, so it is widely used as the bottom paving block and back lining structure in the glass furnaces and the lining of the glass furnaces for producing glass fiber.
During the use, some parts of the glass furnace are required to have good thermal shock resistance. Since the thermal shock stability of the dense zircon brick is bad, it reduces the service life of glass furnaces and increases the repair cost of glass furnaces.
Zircon can improve the properties of dense zircon brick. The dense zircon brick is made of zircon powder by adding high pure industrial zirconia, fused stabilized zirconia and desilicated zirconia. After Formulating according to the amount of the added zirconia, wet-mixing, spray granulation, isostatic pressing and sintering at 1530 ℃ and 12h insulation, 69% dense zircon brick is made.
Research about these three different samples of zirconia on the apparent porosity, bulk density, firing shrinkage and thermal shock stability and a scanning electron microscope (SEM) on the microstructure and fracture surface samples are carried out.
The results showed that: compared to 65 dense zircon brick without ZrO2 added, the samples with ZrO2 added have higher apparent porosity, bulk density, firing shrinkage and thermal shock stability.

Applications of Fused Cast AZS Block

Fused cast AZS block is made of high pure raw materials in a special electric arc furnace by the casting process of long arc melting and oxidation treatment. There is almost no carbon contamination from the electrodes.
Due to the casting process and high pure materials, fused cast AZS block has super strong corrosion resistance to the glass liquid and low potential of pollution.
Fused cast AZS 33# block has great advantage in preventing the pollution from glass liquid. It can generate stones in glass and has low potential of glass precipitation and bubbling. It is suitable to the upper structure of the melting zone, the sidewall of the work tank, the paving blocks and the forehearth.
Fused cast AZS 36# block is the standard fused cast AZS block made by the oxidizing method. It has special high corrosion resistance to the glass liquid and has low potential of pollution. It is suitable for the areas that are in direct contact with the glass liquid, such as the sidewall of the melting zone, paving block and feed port.
Fused cast AZS 41# block is the highest grade fused cast AZS block. It has the best corrosion resistance to the glass liquid and low pollution potential. It is suitable for the parts that require super high resistance such as the electric melting furnace, throat, kiln dam, bubble block and the corner block of the feed port.

Chemical composition of fire clay bricks

Fire clay brick is the refractory brick containing 30-46% SiO2. It is made of clinkers calcined from refractory clays as the oxidant and bond clay as a binder agent.
The main raw material is refractory clay. Clay is an earthy mineral. It can form plastic mud pie when mixed with water and maintain the shape after drying. It has rock-like hardness after fired at high temperature.
Additionally, the clay contains a certain amount of impurities such as quartz, mica, pyrite, feldspar and organic substances. The impurities, especially iron, can reduce the quality of clay and are harmful to the fire clay bricks.
Alkalis such as Na2O and K2O exist as mica. It can improve the sintering properties of clay and form dense products after sintered. It should be fewer than 2%.
The content of CaO is generally under 11.5% and distributed evenly. So, it will not affect the refractory properties of raw materials.
There is a certain amount of TiO2 in the bond clay. It exists as diamond. When it is less than 1%, it has no big effect on the quality of bond clay. In the chemical analysis, its content is not tested alone but counted in the content of A1203 + TiO2.
When the impurities in the clay exceed 6%, the refractoriness of clay will decease and cannot be used as the raw materials. The content of organic substances in the clay is fluctuated greatly, up to 5%.