Kiln Refractories Blog

Why do Some High Temperature Kilns Use Alumina Bubble Bricks?

June 16, 2021 KilnRefractory

Alumina Bubble Bricks belong to the category of lightweight bricks, and the use ratio is currently not very wide. But why some high-temperature kilns use alumina hollow ball bricks? Refractory manufacturers with rich production and sales experience often provide customers with refractory materials that are most suitable for production needs based on customer requirements and the actual working conditions of high-temperature kilns. This will not only extend the service life of the kiln but also save production costs.

The production process of alumina hollow ball brick. Lightweight hollow sphere bricks are made of alumina hollow spheres as the main raw material, adding ultra-fine powder and other process ingredients to dry and form. It is to add alumina raw material into a dumping electric furnace to melt it into a liquid state, and the furnace is dumped at a certain angle to make the solution flow out of the pouring tank. Then the hollow alumina spheres, sintered alumina fine powder, and binder are mixed according to a certain proportion, formed and fired in a shuttle kiln at a high temperature of 1750°C. Alumina hollow ball brick is a high-grade lightweight refractory material. Its lightweight, high-temperature resistance, small line change, and excellent thermal shock resistance. It can be used as an insulation layer and can be used directly on the working layer.

Why do some high-temperature kilns use alumina bubble bricks? Now in high-temperature kiln equipment, the proportion of heavy refractory bricks used will be larger. However, in order to optimize the structure of some furnaces, it is necessary to reduce the weight of the furnace. The bulk density of high temperature resistant heavy refractory bricks is above 2.6g/cm, and the bulk density of alumina bubble bricks is only 1.1~1.5g/cm. Therefore, in the case of the same cubic meter volume, the use of hollow ball bricks can reduce the weight of the kiln body by 1-2 tons.

From the perspective of cost, the price of heavy bricks and hollow ball bricks are similar. The price of alumina bubble bricks for special areas may be slightly higher than that of heavy bricks. But in terms of weight, the use of hollow ball bricks can reduce 1-2 tons per cubic meter. Moreover, there is no need to make an insulation layer, which reduces the number of use and saves fuel. Not only the use effect is good, but the cost is also reduced a lot.

In addition, because alumina hollow spheres have good thermal insulation properties, reducing heat dissipation improves thermal efficiency, and the energy-saving effect reaches 30%. Therefore, some high-temperature kiln lining high-temperature zone or shuttle kiln lining all use hollow ball bricks, which is light in weight and has a significant effect.

Alumina bubble bricks have high aluminum content, low iron content, and low bulk density. It can be used in the working layer of the shuttle kiln and the tunnel kiln in the high-temperature area, and can also be used as the insulation layer in the high-temperature area.

The above is the reason why some high-temperature kilns use alumina bubble bricks. It can be seen that the choice of refractory materials for certain kilns not only saves costs but also needs to reduce the weight of the furnace body, as well as a good insulation effect. At this time, alumina hollow ball brick is a good choice. If you need to buy high-quality alumina bubble bricks, please contact the refractory manufacturer. Buy directly from the manufacturer, the product quality is reliable, and you can enjoy perfect customer service.

What is the Bulk Density of Refractory Castables?

April 29, 2021 KilnRefractory

What is the bulk density of refractory castables? This is mainly based on the specific construction site and high-temperature resistance requirements. The preparation of refractory castables is customized according to the index requirements provided by users. These indicators mainly include refractoriness, material chemical composition, bulk density, compressive strength, flexural strength, and so on. Bulk density or bulk density is one of the important indicators, which intuitively reflects the compactness of refractory products and characterizes the mass of refractory materials per unit volume. It is an important measure of the quality level of refractory raw materials and dense refractory products.

RS Monolithic Refractory Castable Factory

The Significance of the Bulk Density of Refractories

Bulk density is the ratio of the dry mass of the refractory material to the total volume. The higher the volume density, the higher the density. The bulk density of the material has a significant effect on many other properties, such as porosity, strength, corrosion resistance, load softening temperature, wear resistance, thermal shock resistance, etc. For lightweight thermal insulation materials, such as thermal insulation bricks, light weight castables, etc., the bulk density is also closely related to its thermal conductivity and heat capacity. Generally speaking, the bulk density of the material is high, which is beneficial to its strength, corrosion resistance, wear resistance, and load softening temperature.

Therefore, with regard to the volume density of refractory castables, each manufacturer has its own standards. In order to increase the bulk density of refractory castables, a reasonable ratio of multi-stage particles should be adopted, which should meet the requirement of “large at two ends and small in the middle”. That is, under the premise of not affecting the performance of refractory castables, adding fine powder matrix or using silicon powder to replace part of the binder material, reducing the amount of water added to increase its bulk density.

Bulk Density of Refractory Castables

The bulk density of refractory castables is different depending on the location of use. It is mainly divided into two parts, namely dense refractory castable and light refractory castable. Dense refractory castables are used for parts that are exposed to high temperature, molten slag, scouring, and thermal shock stress. The use of castables with high bulk density can improve structural strength, wear resistance, slag penetration resistance, thermal shock resistance, etc. Lightweight refractory castables are only used for the material of the thermal insulation layer close to the furnace shell, with the main purpose of thermal insulation. Its strength is low, density is small, porosity is high, and it can’t touch slag or chemically corroded parts.

The density of dense refractory castables configured by different materials is different. For example, the bulk density of clay refractory castables is 2.1~2.2 g/cm3. The bulk density of high-aluminum refractory castables is generally 2.5~2.85 g/cm3, which increases with the increase of aluminum content. The bulk density of clay low cement castable is 2.2~2.3g/cm3. The bulk density of corundum low cement castable is 3.0~3.1g/cm3, etc.

The lightweight refractory castables configured by different materials are different. For example, the bulk density of lightweight floating bead castables is 0.6~1.0g/cm3. The bulk density of the castable prepared with clay porous clinker is 0.8~1.3g/cm3. The volume density of the castable configured with mullite porous clinker is 1.2~1.6g/cm3, etc.

In short, the bulk density of refractory castables depends on the temperature and location of use. For example, the bulk density of high alumina refractory castable is 2.5g/cm3 or 2500kg/m3, which means that a cubic high alumina refractory castable weighs about 2.5 tons. The bulk density of lightweight castables is 0.8g/cm3 or 800kg/m3, representing a cubic weight of 0.8 tons. The volume density of refractory castables is the specific manifestation of bulk density, and the weight of materials required for construction parts can be calculated through this index. Refractory castables will inevitably be lost during the construction process. In order to prepare all the materials at one time, the total quantity can be increased by about 0.5 tons to avoid suspension due to insufficient construction materials.

Refractory Castable Manufacturer and Sales Manufacturer

This is the introduction about the appropriate density of the castable. I hope it will be helpful to you. If you have any other questions, please feel free to contact us. Purchasing suitable refractory materials for the kiln lining, and looking for a suitable refractory lining material solution, the strength of the Rongsheng refractory manufacturer is your reliable guarantee. Our experienced technical team and our advanced refractory production line have won us many return customers and long-term cooperative customers. If you have any questions about refractory materials or refractory lining materials, please contact us or follow our blog.

Can the Price of Refractory Bricks be Determined by Color?

April 7, 2021 KilnRefractory

Can the color of refractory bricks determine the price of refractory bricks? is this real? Among the customers I have contacted in the past, I have encountered customers who left messages saying that they want to buy red or black refractory bricks from our manufacturer, as well as those who buy white smooth refractory bricks. Similarly, some purchasing managers are obsessed with buying refractory bricks of a certain color. So can the price of refractory bricks be judged by the color?

Rongsheng Kinds of Refractory Bricks for Sale

After specific communication with customers, they found that some of them are looking at the color of our refractory bricks that are very suitable for the color of their crafts, so they want to buy a certain color of refractory bricks. Their needs are not in line with our goal of serving refractory linings for industrial kilns. And when customers learned that we were providing refractory brick materials for the lining of industrial kilns, they stopped insisting. Among the refractory bricks lined with industrial kilns, the color of the refractory bricks reflects the proportion of the refractory raw materials added to a certain extent and has a certain influence on the properties of the refractory materials. Similarly, it also affects the price of refractory bricks.

The Colors of Some Common Refractory Bricks

People who are often exposed to refractory materials can basically judge the material of refractory bricks based on the color. The color of fireclay refractory bricks is generally light yellow or brownish yellow, dark yellow, and there will be brown or black spots on the surface of the brick. This is generally a spot formed by impurities in the refractory raw material after being fired at a high temperature. The color of high-alumina bricks is mostly beige, and even a little whitish. Refractory brick products made of magnesia, graphite, and silicon carbide are mostly blue. Corundum and mullite are mostly white.

High alumina bricks are often used to judge the quality and grade of bricks by color. In fact, the color of refractory bricks with the same index content will also appear inconsistent. This is because there are many factors that affect the color of refractory bricks.

① The bricks are unreasonably stacked when loading the kiln car, and the sparseness and unevenness cause the flame to not uniformly heat all the bricks. The bricks are heated unevenly during preheating, and the moisture of the refractory bricks cannot be completely eliminated and enters the firing zone, causing some refractory bricks to appear different in color and light.
②The processing temperature of refractory bricks is not well controlled, resulting in too much fluctuation of the firing temperature, which will make some parking spaces have high temperatures and some low temperatures.
③If the pulling force of the smoke exhauster is too large, when the flame cannot reach the top of the kiln, it will be pulled out of the high-temperature zone by the pulling force in a horizontal direction, causing the temperature difference between the top and the bottom to be too large. The temperature difference of the fired refractory bricks can reach 50 degrees so that sometimes the lower part sticks and deforms to produce waste products, but the upper part still does not reach the sintering temperature.

In addition to the influence of the process during the firing process, after the refractory bricks are discharged from the kiln, with the influence of the storage time and storage environment, some chemical reactions will gradually occur on the surface of the refractory bricks, which will eventually cause the color difference of the refractory bricks.

There are more factors affecting the appearance and color of fused-cast refractory bricks, such as the oxidizing atmosphere and reducing atmosphere when the batch material is melted, and the degree of solubility of impurities during the conversion process.

How Can I Buy High-Quality Refractory Bricks?

Having said that, what should be the standard when buying refractory bricks? First of all, we must know that there are corresponding national standards for the appearance of refractory brick products. “GB/T 10326-2016 Inspection Method for Dimensions, Appearance, and Section of Shaped Refractory Products”, this standard is required from the appearance of refractory bricks.

Secondly, when we buy refractory bricks, we must look at the content of the material, the main material, and the content of impurities. Because generally, shoddy manufacturers will make a fuss about the ratio of raw materials and materials, such as materials with a low main material content, such as the wrong proportion of materials, such as materials with more impurities, and so on. After this type of brick is produced, the surface will generally be rougher and the color will be uneven. The purchaser may require the supplier to provide the inspection report or quality certificate of the goods at the time of purchase. The test report of refractory bricks can reflect the content, porosity, refractoriness, load softening temperature, compressive strength, and other values of this batch of bricks.

Finally, in addition to the content detection, because refractory bricks also involve bulk density, specifications, and dimensions. Therefore, some manufacturers also have unit weight or body density requirements when purchasing. Because, based on the unit weight, we can also make a rough judgment on the quality of refractory bricks.

To learn more about the recognition and identification of the color of refractory bricks, please start with the basic knowledge of refractory materials. Our blog not only introduces our products to you but also introduces you to the relevant knowledge of refractory materials at any time. Please pay attention to our blog to know why there are black spots, black hearts, or cracks in refractory bricks at any time? You can also understand the requirements of binders and additives in the production of refractory bricks of different materials, and so on.

Combination Method of Alumina-Magnesia Castable

March 18, 2021 KilnRefractory

In recent years, due to the vigorous development of out-of-furnace refining technology and continuous casting technology, the ladle is also used as a vessel for holding molten steel and molten steel refining equipment, which greatly extends the residence time of molten steel in the ladle. This is accompanied by an increase in the tapping temperature and more severe smelting conditions. As a result, the service life of the inner lining of the ladle is greatly reduced. The ladle uses alumina-magnesia castables, including spinel-containing castables, and it has always been a development trend for integral casting.

High-Quality Alumina-Magnesia Refractory Castable

The Combination Method of Alumina-Magnesia Castable

Binder is an important part of alumina-magnesia castables. The bonding methods used for alumina-magnesia castables are generally calcium aluminate cement bonding, silica micro-powder bonding, hydrated alumina bonding, sol bonding, magnesium silicon water bonding, and so on.

Cement bonding

At the initial stage of development of alumina-magnesia castables, pure calcium aluminate cement is used. This is because the cement calcium aluminate will react with the Al2O3 in the matrix to form CA6, which is a highly refractory phase. However, as the number of cement increases, the fluidity of the castable decreases. At the same time, due to the excessive content of CaO at high temperatures, it will react with SiO2, Al2O3, and MgO in the matrix to generate a low-melting phase, which will reduce the high-temperature performance of the castable. Some refractory researchers have studied the effect of the amount of water added in cement on the thermal expansion behavior of alumina-magnesia castables after high-temperature firing. The results show that with the increase of cement addition, the phases of CA2 and CA6 in the sample increase, and the linear change rate of the sample after high-temperature heat treatment increases. In addition, some people have studied the influence of silica powder, magnesia, and cement on the properties of high-purity alumina-magnesia castables. The study pointed out that the pure calcium aluminate cement and the Al2O3 fine powder in the matrix start to react at about 1000°C to form CA2 and CA6, and the reaction is accompanied by volume expansion. It can reduce the intensity ratio after high- and medium-temperature firing, and also contribute to the improvement of the high-temperature performance of the sample.

MgO-SiO2-H2O combination

There are many kinds of researches on the combination of MgO-SiO2-H2O. The combination of MgO-SiO2-H2O is used in the alumina-magnesia castable. On the one hand, due to the polymerization of SiO2 gel formed by the interaction of SiO2 powder and water, the amount of water added is reduced, and the fluidity of the castable is greatly improved. On the other hand, the combination of MgO-SiO2-H2O can inhibit the hydration of magnesia, but too much silica powder will form a low-melting phase with impurities in the matrix. At the same time, the forsterite phase formed by the reaction of magnesia and silica powder in the matrix has poor thermal shock stability at high temperatures.

Composition Materials and Properties of Low Cement Alumina-Magnesia Refractory Castables

The slag resistance of low-cement alumina-magnesia refractories is similar to that of alumina-magnesia spinel castables but superior to alumina-spinel castables. Therefore, it is selected by users at home and abroad, especially in the Japanese steel ladle. In addition, the material is used in the desalinization pouring channel of the large-scale blast furnace tapping channel, and its life is longer than that of the Al2O3-SiC-C iron channel material.

The high-tech basis of low-cement alumina-magnesia refractory castables is high-grade raw materials and scientific formulas. Construction, baking, and careful process operation and maintenance are the guarantees of its long life. This material is used on a ladle of about 100 tons, and the ladle age is 60 ~ 120 times.

The performance of low cement alumina-magnesia refractory castables is excellent. The content of MgO is not more than 8%, and the content of Al2O3 is 89% ~ 97.6%, indicating that the material is excellent. The linear changes after firing are all positive values, the pores are low, and the strength is high, which is beneficial to the use of castables.

Low-cement alumina-magnesia refractory castables are developed on the basis of sodium silicate alumina-magnesia refractory castables and have been used on medium and small ladles with good results. When higher-grade refractory raw materials are used and the material formula is designed with scientific methods, high-tech low-cement alumina-magnesia refractory castables can be successfully formulated. It can be used on large and medium-sized ladle to improve the age of the ladle.

For more detailed information about refractory castables for kiln furnaces, please visit the website of Rongsheng Kiln Refractories Website: https://kilnrefractory.com/.

How to Choose Refractory Plastic or Low Cement Castable for the Top of the Heating Furnace?

March 2, 2021March 2, 2021 KilnRefractory

Use refractory plastics or low cement castables in different areas of the heating furnace roof? The temperature of the heating furnace varies greatly from the preheating section, heating section, and soaking section, and each part has different functions. When choosing plastic refractory or low-cement castables, the use performance and price factors must be considered, as well as the convenience of construction and the storage of products.

Unshaped Refractory Material for Heating Furnace Roof

Refractory plastic can not damage its packaging before construction. If the packaging material is damaged, the plastic can lose its plasticity. When storing and keeping the plastic, pay attention to the integrity of the plastic packaging.

If low cement castables are used, anchors must be welded. If the plastic material is fixed on the furnace roof by anchoring bricks, the tightness of the plastic material and the anchoring brick affect the quality of the plastic furnace roof.

Ramming around the anchor is very important when the fire-resistant plastic is constructed. Make wooden molds based on the shape of anchor bricks. When the plastic is rammed, a wooden mold is used to mold the plastic around the anchor bricks, and then the anchor bricks are inlaid in the mold. Pram around the anchor brick with the wind to make it come in close contact with the plastic. But be careful not to smash the anchor brick.

But plastic is more shrinking. After removing the mold, use an expansion joint knife to cut a 30-50mm expansion suture on the surface with an interval of about 1.5m, which means that the plastic surface is cut into 1.5m square blocks. But if the plastic shrinks, it will only crack in the opened expansion joint, and no cracks or cracks will appear.

If low cement castables are used, 20 anchors per square must be welded. Support the mold first, then pour the low-cement castable, take off the film after 24 hours, and then grill according to the barbecue system.

In short, whether fire-resistant plastic or low-cement castable is used, depends on the situation. If there is no condition to store plastics, low cement castables can be used. If the construction of low cement castables is inconvenient, refractory plastics can also be used.

How Long is the Setting Time of the Refractory Plastic?

Refractory plastic is an amorphous material that can maintain good plasticity for a long time. Next, we come to understand some characteristics of the refractory plastic from the setting time of the refractory plastic.

$The Setting of Refractory Plastic$

The refractory plastic can be in the form of a mud paste, or it can be separated from the powder and the binder. If you are in a hurry for construction or repair, it can be made into a mud paste. If the construction time is long, the powder and the binder can be packaged separately, so that they can be mixed and used during pre-construction.

The plasticity of the plastic has a great influence on the bonding strength and volume stability of its hardened body. It is the properties of clay that control the properties of refractory plastics. The plasticity is related to the properties and dosage of the clay, which increases with the increase of the binding dosage. If the binding dosage is too high, the fire resistance and plasticity are not strong, and it is best to control it at 5%-10% so that the plasticity of the plastics will not decrease during the shelf life. The binding agent is a special glue preparation.

The refractory plastic can be taken out from a sealed container during construction, or a special bonding agent can be added on-site to trap the material. The trapping time cannot be less than 10 hours. Then lay it between the hanging bricks or anchoring bricks and tamping with a hammer. In particular, the plastic can be processed into any shape before being hardened.

Refractory plastic In order to facilitate the drainage of water, holes should be punched at regular intervals. Expansion joints should also be set according to the design. If the part to be constructed is integral, first construct on the bottom form and then hoist it after drying.

The setting time of refractory plastic is 1-3 hours for the initial setting and 6-8 hours for the middle setting. It can reach 60-80% strength after one day of curing, 85%-95% of the strength is reached after 3 days of curing, and it can be used after 7 days of final strength.

Unshaped Refractory Material Sales

Rongsheng refractories production and sales factory have advanced and fully automatic monolithic refractory production lines. The annual output is 80,000 tons. Our unshaped refractory products mainly include various refractory castables, ramming mass materials, refractory plastics, low cement castables, wear-resistant refractory castables, etc. We can customize the formula of unshaped refractory materials according to the specific needs of customers. Our monolithic refractory products have a high rate of return orders from our monolithic refractory customers. Customers’ trust in us stems from our strict control of product quality. And we are committed to providing customers with high-quality customer service. To purchase high-quality unshaped refractory products, please contact us. We will provide you with the most suitable products for your project production needs according to your specific construction needs.

Methods of Increasing the Service Life of Silica Bricks in Glass Melting Furnaces

November 26, 2020 KilnRefractory

Traditional and new refractory materials are used for glass kiln construction and repair. Traditional refractory materials for industrial use include clay bricks, dense clay bricks, mullite silica bricks, mullite bricks, mullite corundum bricks, and corundum bricks. High-temperature insulation materials and high-purity magnesium spinel refractory materials. Unshaped refractories include plasticized aluminum silicate cement, high-alumina cement, and low-cement castables.

The use of refractory materials in glass melting furnaces. Silica bricks are widely used in glass melting furnaces, and the main component is silicon dioxide (SiO₂). The silica brick used in the glass melting furnace requires a SiO₂ content of 94% or more, a maximum operating temperature of about 1600~1650℃, and a density of 1.8~1.95g/cm³. The apparent porosity is required to be less than 22%. The larger the porosity, the worse the quality of the silica brick. The appearance of silica bricks is mostly white crystals, and the microscopic composition is tridymite crystals. Because silicon bricks undergo crystallization conversion and volume expansion at high temperatures, especially at 180~270℃ and 573℃, the crystallization conversion becomes more intense. Therefore, in the process of the baking kiln and cold repair, it is necessary to adapt to the crystal transformation of silica bricks and take appropriate measures such as elastic strips. The silicon brick masonry should be left with expansion joints.

How to Improve the Performance of Silica Brick in a Glass Kiln

The advantages of siliceous materials are high-temperature strength, good creep resistance, low density, no pollution to glass, and low price. The working temperature of silica bricks is about 200℃ higher than that of clay bricks, but the corrosion resistance to molten glass and alkaline flying materials is poor. Therefore, it is used for masonry structures such as masonry, parapets, and small furnaces. When masonry, use high-silicon refractory mud or silica brick powder and other materials close to the composition of silica bricks as the cementing material.

Ways to Improve the Life of Silica Bricks

In the 1980s, my country introduced advanced silicon brick manufacturing technology for glass kilns from the United States. In order to distinguish it from the original product, the product manufactured with imported technology is called high-quality silica brick. The composition (W) of high-quality silica bricks is cristobalite 45%, phosphorite 50%, glass phase 1%~2%, and a small amount of residual quartz. Melt index (2R2O+Al2O3)<0.5%.

After adopting oxy-fuel combustion technology, the life of silica bricks has been drastically reduced from 5 to 10 years to 2 to 3 years. Rat holes and erosion are the main causes of damage. The rat-hole is caused by the alkali in the gas leaking from the kiln condensing in the cracks of the brick to corrode the silica brick. The methods to improve the life of silica bricks are as follows:

1) Improve the dimensional accuracy of bricks. Control size tolerance <0.5mm, brick gap width <1.5mm. The cracks between the bricks are narrowed, the kiln gas leaks less, the erosion is light, and the mouse hole is also small.
2) Reasonably design the kiln lining structure. Move the condensation temperature zone of the alkali to the sealing layer behind the silica brick.
3) Use low-calcium silica bricks with good corrosion resistance (w(CaO)≈0.8%). Figure 4 shows the corrosion resistance test results of low-calcium silica bricks and high-quality silica bricks. It can be seen from Figure 1 that when the alkali vapor pressure is low, the corrosion resistance of low-calcium silica bricks is better than that of high-quality silica bricks.

The influence of alumina content on the performance of silica brick for glass kiln

The increase of Al2O3 content is unfavorable to the refractoriness, softening temperature under load, true density, and mineral composition of the product. But it has no obvious influence on the apparent porosity, residual line change, and creep rate.

Development of High-Purity, Corrosion-Resistant Glass Kiln Silica Brick

China’s glass output has ranked first in the world. The main task for the future development of refractory materials for glass kilns is to improve the design, masonry, and maintenance of the kiln, reduce the adverse effects on the quality of glass, and extend the service life of the glass kiln. Silica brick is the main refractory material in the masonry of the glass furnace and is mainly used for the ceiling, hanging wall, and front and back walls of the glass furnace. To increase the service life of glass furnaces, higher requirements must be put forward on the quality of silica bricks. Therefore, the study of high-quality silica bricks for glass kilns with high purity and corrosion resistance can extend the service life of glass kilns to a certain extent.

Rongsheng Refractory Brick Manufacturer

Rongsheng refractory brick manufacturer is an experienced refractory material manufacturer and sales manufacturer. Rongsheng’s refractory products have been sold to more than 60 countries and regions all over the world. For example, Russia, South Africa, Kazakhstan, Philippines, Chile, Malaysia, Uzbekistan, Indonesia, Vietnam, Kuwait, Turkey, Zambia, Peru, Mexico, Qatar, etc. Obtain high-quality refractory products for glass kilns, such as AZS bricks, silica bricks, fused corundum bricks, checker bricks for regenerators, etc. Please contact us, we will provide you with services according to your specific needs.

A Widely Used Refractory Material – Fireclay Refractory Bricks

October 27, 2020October 27, 2020 KilnRefractory

Fireclay refractory bricks refer to fireclay products with Al2O3 content of 30%-40% alumina silicate. The refractory temperature is 1690~1730℃. It has good thermal stability, and the number of times of water quenching and heating is 10-25 times, and it increases with the increase of clinker and coarse particle content. Refractory clay bricks are weakly acidic refractory materials, which can resist the erosion of acidic slag, but their resistance to alkaline slag is slightly weaker. Among all refractory materials, refractory clay bricks have the widest application range. For example, the protective bodies of various heating furnaces, heat treatment furnaces, cupolas, and drying furnaces are mostly built with refractory clay bricks. In addition, fireclay refractory bricks can also be used to build steel drum linings.

Rongsheng Fireclay Refractory Bricks for Sale

Refractoriness of Lightweight Fireclay Refractory Bricks

Lightweight fireclay bricks are lightweight refractory products with a porous structure with an AL2O3 content of 30%-46%, which are shaped refractories. Mainly use plastic mortar burnout additives or mortar foam method or chemically made porous products. The product has a wide range of uses and can be used for the thermal insulation layer of various high-temperature furnaces.

The specifications and sizes of lightweight fireclay bricks are divided into standard and special shapes. Standard specifications are available at Rongsheng refractory brick manufacturers, and special-shaped specifications and sizes can be customized according to drawings. Lightweight fireclay bricks are characterized by high porosity, uniform pore distribution, low volume density, good stability, and excellent thermal insulation properties.

Indicator of light fireclay bricks. The bulk density of commonly used lightweight fireclay bricks is 0.75-1.2g/cm3. The smaller the bulk density, the better the thermal insulation, and the lower the use temperature. The compressive strength is 0.98-5.88MPa, and the abrasion resistance is poor. It should be handled with care when handling or building. The thermal conductivity at 300°C is 0.795-2.93W/(m.k). The operating temperature is generally 900-1250°C, and the maximum operating temperature is 1200-1400°C.

The use temperature of light fireclay bricks of different bulk density has certain differences, and the price is also different. Therefore, the choice of light clay bricks depends on the operating temperature of the kiln and is based on the economy and practicality.

Masonry of Clay Refractory Bricks

Before choosing fireclay refractory bricks to build the furnace, the factory can calculate the approximate quantity needed to purchase in the furnace building plan. It can reduce unnecessary waste, and pay attention to the use of first-grade mortar joint masonry for masonry mortar joint.

When building clay bricks, it is feasible to prepare clay refractory mortar by yourself, clinker: raw material = 70%: 30%. Clinker is obtained by calcination of hard refractory clay at high temperatures. Waste bricks can also be used after being ground. The raw meal is light refractory clay.

If you want to calculate the various compositions of refractory mortar, just substitute the known weight of refractory mortar into formula (1) and formula (2).

(1) Clinker weight = refractory mortar weight x 70%

(2) Raw meal weight = refractory mortar weight x 30%

When using T-3 standard bricks (230x114x65mm) for masonry. The following figures should be memorized:

Each refractory clay brick weighs 3.7kg.
About 270 pieces of refractory clay bricks per ton.
Each ton of clay bricks requires about 76kg of refractory mortar.
It takes about 594 bricks per cubic meter of masonry.
Approximately 2.2 tons of bricks are required for each cubic meter of masonry.

Rongsheng Fireclay Refractory Bricks Manufacturer

Rongsheng T-7 Fireclay Refractory Bricks Manufacturer

T-7 fireclay refractory brick, unit weight 4.1kg, alumina oxide is greater than or equal to 65. Zhengzhou Rongsheng Refractory Material Factory fire clay bricks for sale mainly produces various types of high alumina and fireclay refractory bricks, low creep high alumina bricks, high alumina balls, corundum bricks, light insulation bricks, and magnesia carbon bricks. Refractory mortar for all kinds of kiln masonry, unshaped refractories of various materials for smelting and steelmaking. Shaped refractory products and unshaped refractory materials can be produced in accordance with general standards and special requirements of users. Contribute to the longevity, high-quality, high-yield, energy-saving, and consumption reduction of high-temperature industrial furnaces!

How to Improved the Performance of Low Cement Castables

September 26, 2020 KilnRefractory

The low cement castable in the unshaped refractory is a castable with a CaO content of less than 2.5% in the refractory castable combined with calcium aluminate cement. That is to say, the amount of calcium aluminate cement added is about 1/2 to 1/3 of the castable of ordinary calcium aluminate cement. Rongsheng refractory material manufacturer has advanced and fully automatic monolithic refractories material production line. Next, let’s understand the use and advantages of low cement castables, as well as the performance improvement of low cement castables.

Application of Low Cement Castables

Low cement castables are mainly used in metallurgy, electric power, nonferrous metals, petrochemical, building materials, and other industries. Such as the bottom of the glass kiln, the front end of the front and rear kiln door cover coolers of the cement kiln, and other high-temperature resistant parts, the front, and rear kiln mouths, coal injection pipes, etc. Various heat treatment furnaces such as heating furnace and soaking furnace. Intermediate frequency induction furnace lining, the high-temperature wear-resistant lining of the petrochemical catalytic cracking reactor, lining of other industrial furnaces, etc. The construction methods of on-site pouring, smearing, and ramming can be used.

Rongsheng Low Cement Castable Manufacturer

Advantages of Low Cement Castables

Different from traditional refractory castables, the matrix of low-cement castables replaces part or most of the calcium aluminate cement with superfine powder with the same or similar chemical composition as the main material of the castable with a cohesive bonding effect. Therefore, low cement castables are castables that coexist with hydration and cohesion. Due to the use of ultrafine powder (micro powder) to replace part of calcium aluminate cement, low cement castables have the following advantages.

The low content of CaO in the castable can reduce the formation of the eutectic phase in the material. Thereby improving the refractoriness, high-temperature strength, and slag erosion resistance.
The mixing water consumption of the castable during construction is only 1/3~1/2 of the ordinary castable, so the porosity is low and the bulk density is high.
After pouring and molding, less cement is generated during curing. Therefore, there is no damage to a large number of hydration bonds during heating and baking, resulting in a decrease in the medium temperature strength. But as the heat treatment temperature increases, the strength gradually increases.
With proper adjustment of the strength and composition of the castable, it can be formulated into self-flowing castable and pump castable.

Improve the Performance of Low Cement Castables

Low-cement castables have the advantages of less water addition, high density, good volume stability, and high strength, so they are widely used. However, due to its poor air permeability, it is prone to bursting, peeling, and peeling during baking and ignition. Severely, it even leads to the overall destruction of the construction body, causing serious losses to users. Therefore, how to improve and increase the explosion-proof performance of low-cement castables is of great significance to the practical application and development of low-cement castables. At present, the main method to improve the explosion-proof performance of castables is to add explosion-proof fibers to the castables to increase the permeability of the castables.

Studies have shown that the increase in the amount of explosion-proof fiber has a significant effect on increasing the apparent porosity of low cement castables and improving the explosion-proof performance of low cement castables. The reduction of the content of silicon carbide has an effect on improving the burst resistance of low-cement castables, but the effect is not significant. The increase of the content of silicon carbide has a significant effect on improving the thermal shock stability of the low cement castable heat-treated samples at 1400℃.

To learn more about refractory products, please visit our website: https://kilnrefractory.com/.

Learn More About Refractory Castables for Kiln Hood

September 15, 2020 KilnRefractory

During the cement clinker calcination process, the kiln hood is located at a very special position, and it rotates rapidly with the kiln body and is affected by rapid changes in temperature and heat. Therefore, the Refractory Castables for Kiln Hood is a part that needs to be paid attention to and maintained in production.

Why the Refractory Castables for Kiln Hood the Short Service Life?

The castable at the entrance of the kiln is at the end of the rotary kiln. It is easy to cause a large temperature difference in a short time, causing cracks in the traditional Refractory Castables for Kiln Hood. In severe cases, a large area of castable will fall off.

The axial thermal expansion of refractory bricks in the kiln is quite large. If no corresponding measures are taken, the axial stress generated is very surprising. Take magnesia bricks as an example. When the barrel is fired at 300°C, the brick will expand by as much as 50mm than the barrel. When the inner surface of the lining material reaches 1300°C and the outer surface reaches 200°C, the thermal stress of up to 660Mpa will be formed. This huge thermal stress acts on the front kiln hood, causing the back iron to tilt outward, which in turn causes the refractory to loosen and fall off.

The high-temperature clinker continuously scours and abrades the kiln hood part of the cement kiln, making the Refractory Castables for Kiln Hood mechanical damage more intense. In addition, because the metal shell of the kiln is not completely rigid, the ellipticity of the kiln is also affected. Large or small deformations occur in the kiln shell during rotation, causing compression, tension, and shear stress in the kiln lining. Coupled with the continuous relative displacement and local stress between the refractory bricks in the kiln, the castable at the kiln hood fractures and peels off.

Based on the above-mentioned reasons, the conditions for using the lining at the kiln hood are very harsh, and the requirements for Refractory Castables for Kiln Hood are extremely high.

RS Steel Fiber Refractory Castable Manufacturer

Refractory Castables for Kiln Hood

The Refractory Castables for Kiln Hood include corundum steel fiber castable, kiln hood anti-stripping castable, new-type low-expansion castable, high-strength explosion-proof castable, and corundum mullite castable.

The corundum steel fiber castable is made of high-density, high-melting, tabular corundum as the main raw material, which has the excellent high-temperature performance. The high-temperature alkali resistance is good, and the alkali resistance level at 1350℃ can reach above level 2, which solves the problem of poor alkali corrosion resistance of corundum castables. It has good thermal shock stability and avoids the phenomenon of product peeling and falling off during use.

The kiln hood anti-stripping castable adopts in-situ synthesis reaction technology. The mullite phase is formed in the material matrix part at high temperatures to improve the high-temperature thermal strength of the material. Improve the material structure and mineral composition, and improve the thermal shock stability of the material. The material has a strong resistance to erosion and abrasion at high temperatures. It has excellent alkali resistance, and the alkali resistance level at 1350°C can reach level 2 or higher. The material is moderately priced, cost-effective, and has good results.

The high-strength explosion-proof castable uses raw materials with high purity, low impurities, and high refractoriness. In addition, the composition of the matrix is strictly controlled, and the mullite crystal phase is formed at high temperatures, which improves the thermal strength of the castable and has good thermal shock stability. It also enhances the anti-erosion performance and wear resistance of the castable, and extends the service life. This product is an explosion-proof castable with good anti-cracking performance and can meet the needs of emergency repairs.

Corundum mullite castable is also called corundum mullite wear-resistance castable. The refractory raw materials of corundum and mullite contain abrasion resistance, so they are refractory castables named after raw materials and properties. The characteristics of corundum and mullite castable have the common advantages of corundum and mullite castable. Part of the matrix reacts in situ to form a mullite phase at high temperature, which improves the high-temperature thermal strength and thermal shock stability of the cast lining. It has high temperature and high compressive strength, thermal shock resistance, and structural peeling resistance. Good high-temperature volume stability and thermal shock resistance, high load softening temperature, low high-temperature creep rate, and good chemical corrosion resistance.

Corundum Mullite Refractory Castable For Sale

Rongsheng Refractory Castable Manufacturer

Rongsheng is a manufacturer with advanced refractory castable production lines. Rongsheng’s monolithic refractories workshop adopts a fully automatic production line with an annual output of 80,000 tons. In the same industry, it is in the leading stage. In the process of accumulating many years of production and sales experience, Rongsheng Kiln Refractory Manufacturer is recognized by customers in more than 60 countries around the world. For more information about Rongsheng refractory manufacturers, or to purchase refractory castables for kiln hood, please contact us. We will provide you with services according to your specific needs.

Preparation of 65% Zircon Brick

July 17, 2020September 15, 2020 KilnRefractory

Zircon (ZrSiO4) belongs to the tetragonal system. The theoretical composition is 67.2% of Zr02 and 32.8% of SiO2, which is the only compound in the binary system of Zr02-Si02. 65% Zircon Brick. The thermal expansion coefficient is small, the load softening temperature is high, the thermal shock stability is good, and the thermal conductivity decreases with increasing temperature. Therefore, As the refractory materials manufacturer said, the zircon refractory brick is an indispensable material for industrial kilns such as building materials, light industry, electronics, metallurgy, and so on.

In recent years, with the advancement of glass industry technology and the application and promotion of kiln insulation technology, the amount of machined 65% Zircon Brick has been increasing. Mainly used in the gap, upper partition wall, fire observation hole, temperature measurement hole, and other parts of the glass kiln. The temperature of this part is high and it is eroded by flying materials and eroded by hot airflow, so the environment is very engraved.

RS Zircon Refractory Bricks Manufacturer

Preparation of 65% Zircon Brick

To produce zircon bricks with a Zr2O3 content greater than 65%, the content of the raw material Zr2O3 used must be greater than 66%. The decomposition temperature of the zircon is 1676℃. As the content of impurities increases, the decomposition temperature decreases. The high purity of the raw materials is the primary condition for the production of zircon refractory bricks with 65% zirconium with excellent properties.

The raw material of zircon is granulated and cannot be directly used for making bricks, but must be ground into a fine powder. Because zirconite has a large wearability index, the fine powder is obtained by vibrating mill and air-jet mill.

Due to the use of 65% zircon brick containing ZrO2. The material should have good high-temperature physical properties, and the aggregate is closely related to it. The zircon sand is ground first, then made into a green body, which is crushed into different particle sizes after high-temperature calcination. Because the zircon material is brittle, the broken particles are in the form of flakes. The normal temperature compressive strength of sheet materials is about 50% higher than that of granular materials. On the contrary, under the same conditions, the bulk density of granular granules is 0.12g/cm³ higher than that of flakes on average. Taking into account the compressive strength and density performance, the crushed material must be properly treated before it can be used.

The batch materials are mixed on a wheel mill mixer, and the materials are trapped for 16 hours, and then formed on a large-tonnage friction brick press. The forming pressure is 700~1000Kg/cm³. Applying large pressure can cause the average distance between adjacent particles to decrease and the contact area to increase, which is beneficial to sintering. But after increasing to a certain level, the effect is extremely insignificant. Appropriate pressure and pressurization methods are the keys to solving the formation of barren materials.

The sintering of zircon is more difficult, and its speed is slow due to solid-phase diffusion at high temperatures. Adding MgO, CaO, Y2O3, TiO2, ZnO2 can reduce the sintering temperature and promote its sintering. In this sintering, 1.5% to 2.75% of Y2O3 and TiO2 were added as sintering accelerator, sintered in a shuttle kiln, and the firing temperature was 1580 to 1650℃.

RS High Quality Zircon Bricks — RS High-Quality Zircon Bricks

Use Performance of Zircon Brick in Steel Ladle

The use performance of zircon bricks in steel Ladles is also called zircon bricks in steel Ladles. It is made of zircon as the main raw material and participates in the combination of a certain amount of fused alumina, high-silica content of clay soil, clay, and chromium oxide. This kind of steel barrel lining bricks has been developed abroad for a long time. In order to improve the uneven erosion of semi-silicon brick steel lining bricks, it gradually expanded from strengthening local lining to all lining bricks. As a result, the service life of large steel Ladles is increased by 2 to 3 times. In order to meet the use of the first phase of Baosteel in China, this brick has been developed and used.

The defects of zircon bricks are slag, steel, and spalling. The main reason is that it is not easy to reduce the porosity due to the zircon brick, and it is affected by the infiltration and the glass property generated in the matrix part. The advantage is that the service life can reach more than 100 times, which is conducive to the turnover of the steel drum. The high cost of this kind of brick is also limited by the source of domestic raw materials, which restricts its development.