2021 - RS Kiln Refractory Bricks

In the refractory castable combined with calcium aluminate cement, the castable with CaO content less than 2.5%, that is, the castable with calcium aluminate cement added about 1/2 to 1/3 of the ordinary calcium aluminate cement castable, It is called low cement castable. Low cement castable materials are clay, high alumina, mullite, corundum, chromium corundum, zircon mullite, zirconium corundum, alumina-spinel, and carbon and silicon carbide, and many more. According to its operating performance, it is divided into vibrating castable and self-flowing castable. Rongsheng refractory manufacturer will introduce the above two different types of low-cement refractory castables for you.

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Two Different Types of Low Cement Castable Composition

The ingredients of vibrating low cement castables are generally: refractory aggregate 60% ~ 70%, refractory powder 18% ~ 22%. Calcium aluminate cement 3% to 7% (low cement type) or 1% to 2% (ultra-low cement type). Silica (soot silica) micro powder (or reactive alumina micro powder) 3% ~6%. Trace dispersant. The particle size composition can be according to Andreassen’s particle size distribution equation, and the q value is 0.26 ~ 0.35.

The batching composition of the self-flowing low-cement castable is similar to that of the vibrating low-cement castable, but the particle size composition and fine powder content are different. Generally, the maximum critical particle size of aggregate is not more than 6 mm, and the particle size distribution is in accordance with the Andreassen or Dinger-Funk particle size distribution equation. The value of the particle size distribution coefficient q should be controlled between 0.21 and 0.26, and a larger self-flow value (greater than 180) can be obtained between this value. When the q value is greater than 0.26, the flow value becomes smaller, and it is difficult to cause self-flow. When the q value is less than 0.21, the powder content is too large, which will affect the physical properties of the castable. The content of micro powder (silica micro powder) in the particle size composition is generally 5% ~ 6%. At the same time, high-efficiency dispersants must be used.

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Low Cement Castables Physical and Chemical Indicators

Table 1 shows the typical vibrating low-cement clay, high-aluminum, and corundum casting performance.

Table 1 Vibrating Low-Cement Castables physical and chemical indicators
Items		Clay Low Cement Castable	High-Alumina Low Cement Castable	Corundum Low Cement Castable
w(Al2O3) / %		45	75	92
w(SiO2) / %		50	12	5
w(CaO) / %		＜1.8	＜1.5	＜1.5
Bulk Density / g/cm3	110℃, 24h	2.30	2.60	3.00
Bulk Density / g/cm3	1350℃, 3h	2.26	2.61	3.10
Compressive Strength / MPa	110℃, 24h	72	75	85
Compressive Strength / MPa	1350℃, 3h	90	115	125
Linear change rate after burning / %	1000℃, 3h	-0.3	-0.2	-0.2
Linear change rate after burning / %	1350℃, 3h	±0.3	±0.5	±0.5
Max Use Temperature / ℃		1450	1600	1700
Mixing Water Demand / %		6.0 ~ 6.5	6.0 ~ 6.5	4 ~ 5

Table 2 shows the general self-flowing low-cement alumina-spinel casting performance.

Table 2 Self-Flowing Low-Cement Alumina-Spinel Castable
Items		A	B	C
w(Al2O3) / %		90	88	85
w(MgO) / %		6	6	6
w(CaO) / %		3	5	8
Bulk Density after Burning / g/cm3	110℃, 24h	3.20	3.10	3.05
	1000℃, 3h	3.10	3.08	2.92
	1600℃, 3h	3.15	2.95	2.86
Flexural Strength after Burning / MPa	110℃, 24h	6.5	9.5	10.0
	1000℃, 3h	5.5	7.6	7.8
	1600℃, 3h	30.0	21.5	20.5
Linear Change Rate after Burning / %	110℃, 24h	–	–	–
	1000℃, 3h	0.1	0	0
	1600℃, 3h	-0.1	+0.8	+0.9
Amount of Water / %		4.8 ~ 5.4	5.4 ~ 5.8	5.5 ~ 6.5
Self-Flow Value / mm		＞ 185	＞ 185	＞ 185

Low Cement Castable Refractory Material Application

Low cement castable refractory materials have a wide range of applications. In metallurgy, petrochemical, machinery manufacturing, electric power, building materials, and other industrial kilns, such castables have been widely used to replace some traditional fired refractory brick products as linings. Vibration-type low cement castable refractory materials are mainly used as thick-sized linings. Such as heating furnace, various heat treatment furnace electric furnace cover shaft kiln, rotary kiln, blast furnace tapping channel, ladle, hot metal ladle, etc. The self-flowing low cement refractory castables are mainly used as thin linings and linings for high-temperature refractory components with metal anchors. Such as the outer lining of the water-cooled pipe of the heating furnace, the lining of the integral spray gun for jet metallurgy, the lining of the immersion pipe of the RH and DH vacuum degassing device, and the air supply element of the ladle (breathable brick). And the high-temperature wear-resistant lining of the petrochemical catalytic cracking reactor.

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Refractory Castables Manufacturers

As one of the refractory castables, the unique advantages of low cement castables play an important role in refractory lining materials. Rongsheng refractory castable manufacturers have rich experience in production and sales. Its advanced environment-friendly and fully automatic unshaped refractory castable production line have an annual output of 80,000 tons. To provide our customers in more than 60 countries with high-quality refractory lining materials. For example, Russia, South Africa, Kazakhstan, Philippines, Chile, Malaysia, Uzbekistan, Indonesia, Vietnam, Kuwait, Turkey, Zambia, Peru, Mexico, Qatar, etc. Rongsheng used to customize low cement castables for customers, ultra-low cement castable, and high customer return rate. To obtain free refractory lining material configuration solutions for high-temperature kilns and solve difficult refractory lining material problems, please contact us. We will customize the refractory lining scheme for you according to your actual production situation.

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Jun 11 2021

Which is the Wear Resistance of Refractory Material?

Wear-resistant refractory materials are usually used under high-temperature conditions. Under high-temperature conditions, the erosion and abrasion of the materials produced by the kiln is an important factor that causes damage to the refractory materials in the lining of industrial kilns. Therefore, it is necessary to understand and master the erosion and wear resistance of the refractory materials selected. First, let us start to understand the wear resistance of refractory materials.

Wear Resistance of Refractory Materials

Many changes in the high-temperature wear resistance of refractory materials vary with temperature and material. It is also believed that the “higher strength, the more wear-resistant” of refractory material, this relationship will exist in similar materials, but this relationship does not necessarily exist between different types of refractory materials. For example, the wear resistance of corundum bricks with a compressive strength of 100MPa is weaker than that of high alumina bricks with a compressive strength of 86MPa. There is also the relationship between the wear resistance of refractory castables and their compressive strength and flexural strength. Some people believe that the higher the strength of high-aluminum castables, the smaller the wear. In practice, it is not found that such a relationship. In short, these are to give users a more comprehensive and in-depth understanding of the wear resistance of refractory materials.

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Wear Resistance of Different Types of Refractories

Rongsheng refractory manufacturers have mastered some rules for their wear resistance in the production of refractory materials and studied the possible influencing factors through the wear resistance of refractory materials of different materials.

The wear resistance of different refractory materials is quite different. According to the abrasion resistance of various refractory materials, it can be roughly divided into three gradients. Silicon carbide refractories have the strongest wear resistance, high-alumina refractories and corundum refractories have intermediate wear resistance, and alkaline refractories, siliceous, and clay refractories have poor wear resistance.

Due to the large difference in alumina content of high-alumina refractories, the wear distribution range is wide. The higher the hardness of the mineral, the stronger its wear resistance. It can also be said that silicon carbide refractories have the least amount of wear. Therefore, wear-resistant and refractory materials are selected for some key corrosion parts. The bonding phase of silicon nitride combined with silicon carbide material has high hardness and high strength, and the bonding phase of refractory clay combined with silicon carbide material has a lower hardness of mullite and glass phase. Therefore, silicon nitride bonded silicon carbide materials have better wear resistance than clay bonded silicon carbide materials.

The wear resistance of high-alumina castables prepared with the same high-alumina bauxite material is better than that of high-alumina bricks, and the difference in wear between the two is about 60%-90%. Similarly, the wear resistance of clay castables will be better than that of clay bricks. The castable adopts micro powder technology and the density of low-cement castables is usually greater than that of the corresponding refractory bricks. Because the castable uses a larger particle size aggregate, and the proportion of the aggregate of the castable is larger, and the aggregate is usually denser and more wear-resistant than the matrix. In order to improve the wear resistance of the castable, the wear resistance of the castable is generally improved by adding silicon carbide.

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Analysis of the Reasons for the Different Wear Resistance of Different Types of Refractories

Factors such as the type of crystal structure of different mineral phases and the size of the lattice energy cause the hardness of their minerals to be different. Atomic crystals of diamond, silicon carbide, and corundum have high Mohs hardness, while ionic crystals of spinel, mullite, periclase, and other hardnesses decrease in order. Graphite has the lowest Mohs hardness due to its layered structure composed of weak intermolecular forces. The higher the hardness of the mineral, the stronger its wear resistance. Therefore, silicon carbide material has a small amount of wear and is the most wear-resistant. Magnesia bricks, magnesia spinel bricks, and magnesia-chrome bricks with periclase as the main phase have a large amount of wear, most of which exceed 10cm³. The wear of graphite-containing aluminum-silicon carbide carbon bricks is relatively large, while that of aluminum-carbon materials with low graphite content or without graphite is relatively small.

The bonding phase of silicon nitride combined with silicon carbide materials has high hardness (Mohs hardness 9~9.5) and high strength. The mullite and glass phases of clay-bonded silicon carbide materials have a lower hardness. Therefore, silicon nitride bonded silicon carbide materials have better wear resistance than clay bonded silicon carbide materials. For the high alumina brick with 76% AL2O3 content and the third-grade high alumina brick with 58% AL2O3 content, the former has high corundum phase content, while the latter has high mullite phase content and low corundum phase content, so the former is more wear-resistant.

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Buy High-Quality Refractory Castables

To learn more about refractory materials, please continue to follow our blog. If you need to buy high-quality refractory castables, such as wear-resistant refractories, silicon carbide castables, corundum castables, please contact a strong and experienced refractory manufacturer. Rongsheng refractory material manufacturer has rich experience in the production and sales of refractory materials. Rongsheng has customers in more than 70 countries around the world, and customers continue to return orders. Moreover, Rongsheng Environmental Protection’s advanced and fully automatic monolithic refractory castables are produced first, with an annual output of 80,000 tons. The quality of Rongsheng’s refractory castables is guaranteed, and it has customer service that satisfies customers. Look forward to working with you.

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Apr 20 2021

Replacement of Checker Bricks in the Regenerator of Coke Oven

For coke ovens that have been produced for many years, the single and main walls of the regenerator will crack, melt, deform or even collapse under the action of temperature and other factors. The checker bricks are easy to be blocked, and even deform and melt at high temperatures. When these defects seriously damage the heating system, the regenerator should be renovated.

Refurbishment of the regenerator will cause the increase and expansion of cracks in the single and main walls due to cold air entering the room, so this is generally not done. In the case of forced renovation, the internal masonry should also be protected from damage, and corresponding insulation measures should be taken. It is also necessary to insist on the continuous operation to shorten the refurbishment time, and when conditions permit, coke oven gas should be used to supply heat to the furnace.

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Sampling View of Checker Bricks in the Regenerator

Due to the long-term workload, the checker bricks in the regenerator of the coke oven will melt and creep. When the situation is serious enough to affect the normal production of the coke oven, it needs to be replaced.

First of all, from the perspective of the creep checker bricks taken out of the coke oven regenerator, the damaged checker bricks have expanded volume, the loose internal structure of materials, and blocked holes. The severely damaged parts are concentrated in the upper part of the gas regenerator, generally, no more than three layers of bricks and the upper layer is the most serious. Moreover, the upper part of each checker brick is more creeping than the lower part. A factory sampled and inspected the clogged checker bricks, and the changes are shown in Figure 1.

Figure 1 Sampling of clogged checker bricks in a factory

Replacement Measures of Checker Bricks in the Regenerator

Before construction, prepare all necessary tools and refractory materials and install temporary low-voltage lights. Use a special iron plate to cover the upper surface of the waste gas pan connected to the refurbished regenerator to prevent the scrapped bricks from blocking the exchange equipment.

In terms of production organization. During the repair, there will be one buffer furnace number adjacent to each other, and the furnace will not be drawn during the repair. The actual coking time of the repaired furnace number depends on the length of the repair time, the maturity of the coke cake, and the temperature of the combustion chamber. The coking time of the buffer furnace number is set at 36h, the second buffer furnace number is set at 30h, and the coking time difference between adjacent furnace numbers is more than 4h. In terms of furnace temperature management, the standard temperature for repairing furnace numbers and buffering furnace numbers should be lowered accordingly. If it is blast furnace gas heating, it needs to be temporarily stopped. In order to ensure that the furnace body in the combustion chamber area is not damaged, the adjacent units and coke sides are used at the same time, and the coke oven gas is intermittently heated, and the temperature should not exceed 1200°C. After the checker bricks are replaced, the coke oven gas is used to heat up for 2 to 3 hours when the temperature is raised, and then converted to blast furnace gas for heating. If there is no coke oven gas, the supply of blast furnace gas will be temporarily suspended during the maintenance period. The specific measures for the replacement of checker bricks in the regenerator are as follows.

①Before construction, compare the plan to be released. Select the coking time in the middle heat number, and remove the pressure measuring hole with a crowbar. For regenerators with heat shields and single (main) wall small furnace columns, the small furnace columns, beams, and heat shields should be removed before the masonry is removed. And close the corresponding blast furnace gas valve and the blast furnace gas valve on the adjacent machine and coke side. Disengage the mound rod from the exhaust gas stroke and adjust the opening of the exhaust plate flap.
②Pick off the wall tiles from the horseshoe cover, take out part of the checker tiles and continue to remove the sealing wall to the end. Hang the windshield above, insert an iron plate into the gap between the two layers of checker bricks under the replaced checker bricks, and block the chute with a thermal insulation fiber cloth.
③Use a single hook to remove the checkered bricks. If the checker bricks are tightly packed with the single and main walls or the checker bricks are melted together, the furnace head can be smashed with a crowbar and then pulled out, and the deep checker bricks can be smashed and taken out with a live joint flat shovel. As the checker bricks are pulled out, the iron plate gradually moves to the depths of the regenerator.
④ There is one layer of checkered bricks on the burner and fire channel, and wooden planks are laid on it, which is convenient for people to enter and remove. The checker bricks are stripped into a ladder shape, with 4 to 5 checker bricks per layer. All three layers of checker bricks above are required to be replaced.
⑤Before installing the checker bricks, clear out the broken pieces in the holes of the checker bricks. Gunning and repairing the cracks of the single and main walls, and using a multi-section blower to blow the checker bricks until the blower inspection is unblocked. When blowing, pay attention to the blowing hole not to face the single (or main) wall, but to move slowly from the outside to the inside and from the inside to the outside of the checkered brick channel. Strip off the checker bricks at the bottom of the burner and clean the dirt in the grate bricks and the small flue.
⑥ Put the slideway into the heat storage room and push the checker bricks in. The checker bricks are required to be close to each other without skewing or falling over. Strive to align the holes up and down, and do not lean against the furnace wall on both sides.
⑦After the checker bricks are installed, build the inner sealing wall first, and apply the grout to the outer surface to seal, and then build the outer sealing wall. After the temperature of the regenerator is normal, joint again, install the protective cover, restore the small furnace column spring tonnage, etc.

Safety Precautions for Checker Brick Replacement

① When stopping and replacing the heating of the furnace number in the regenerator of the furnace number, it is necessary to determine whether the furnace number with the addition and subtraction cock is closed or not, and confirm that the furnace number is correct.
② During the construction period, the fans in the corridor of the regenerator and the temperature measurement platform of the storage roof should be kept running to maintain ventilation.
③ Prevent scalds during the process of peeling off the wall or checker bricks.
④During the construction period, a dedicated person should be assigned to wear a carbon monoxide alarm to monitor the gas concentration on site.
⑤ When working on the storage roof operating platform, prevent the first-class parts from being bumped. After taking out the checker bricks, they should be stacked to prevent them from falling.
⑥ It is strictly forbidden for idlers to walk in the corridor of the regenerator near the construction to prevent injuries from falling objects.

Measures to Prevent Clogging of Checker Bricks

In order to prevent the checker bricks of the coke oven regenerator heated by blast furnace gas from clogging, the following preventive measures should be adopted.

①Purge the gas regenerator with compressed air regularly.
② The dust content of blast furnace gas should be controlled below 15mg/m3.
③The physical and chemical indexes of clay checker bricks for coke ovens should establish standards. The content of Al2O3 and low melting point substances should be appropriately reduced with reference to foreign standards.
④ Semi-silica checker bricks should be used on the top 3~5 layers of the regenerator of the newly built coke oven.
⑤The checker bricks that have been found to be blocked should be replaced immediately and replaced with semi-silica checker bricks.

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Ceramics Refractories

Apr 1 2021

Modern Ceramic Kiln Refractories Manufacturer

In modern ceramic kilns, as important structural materials such as beams and columns, it is required to have good high-temperature resistance, thermal shock resistance, and creep resistance. As a shed, it is mainly required not to pollute ceramic products, and secondly, it is required to have good creep resistance, thermal shock resistance, and high strength properties. As a manufacturer of high-quality refractory materials for ceramic kilns, the Rongsheng manufacturer provides reliable refractory lining materials for ceramic kiln refractory linings.

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Refractory Materials for Modern Ceramic Kilns

Therefore, silicon carbide is selected for the production of important supporting materials such as beams and columns due to its high strength, high thermal conductivity, and high thermal shock resistance. However, silicon carbide may cause some transition metal ions to undergo oxidation-reduction reactions and contaminate ceramics. Generally, oxide materials are not prone to oxidation-reduction reactions. Therefore, cordierite-mullite is selected for the production of low-stress kiln furniture materials such as slabs and backing plates for low-temperature fast-fired kilns due to its good thermal shock resistance. The mullite-corundum material is selected as the kiln furniture material for high-temperature ceramic kilns because of its good high-temperature resistance and creeps resistance.

A kiln or stove refers to a stove used to burn ceramic objects and sculptures or to fuse enamel on the surface of metal objects. It is generally made of bricks and stones. It can be made into various sizes according to needs and can be operated with combustible gas, oil, or electricity. Electric kilns are easier to control the temperature than kilns that use combustible gas and oil, but some potters and sculptors believe that the temperature of electric kilns rises too fast. (When the temperature in the furnace chamber is measured with a pyrometer (PYROMETER) or a temperature measuring cone (PYROMETRIC CONES), it can be seen through a peephole.)

Heavy Refractory Materials for Ceramic Kilns

The earliest refractory materials used in ceramic kilns were mainly heavy refractory bricks. With the continuous improvement of light insulation refractory materials, heavy bricks are basically used in the refractory lining of tunnel kilns, track kilns, and other kilns of building sanitary ceramics. Unless there are special needs, it is no longer used. Heavy refractory materials are still used in corrosion-resistant kilns, such as frit kilns, shuttle kilns for pigments, and rotary kilns. The purpose is to avoid slag drop and good corrosion resistance. Especially in frit kilns, where the materials are in direct contact with refractory materials, heavy refractory materials should be carefully selected, especially in terms of material, density, and thermal conductivity. The characteristics of this type of kiln are just the opposite of those of tunnel kilns and track kilns. Generally, heavy-duty refractory materials are in the inner layer, while medium-quality refractory materials and insulation materials are in the middle and outer layers.

The heavy refractory materials used in ceramic kilns are similar to those in the glass industry, mainly acid refractory bricks, neutral refractory bricks, and some special refractory bricks. The basis for selecting bricks is mainly determined by the firing temperature of the kiln, the atmosphere, the corrosiveness of the molten material, and the acidity and alkalinity.

What are the Insulation Materials Used in Ceramic Kilns?

The classification of ceramic kilns is very wide. There are differences in shape, heating method, and firing temperature, but they require a lot of insulation materials. Mullite insulation bricks are needed on the inner wall and backing of the hot surface of the kiln. Because of low thermal conductivity, high-temperature resistance, good stability, fine size, it can be processed into various shapes. Therefore, it is suitable for the thermal insulation of the roof, body, and bottom of industrial kilns, and the appearance is beautiful.

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(1) Mullite insulation brick

Lightweight mullite bricks, also known as mullite lightweight insulation bricks, are high-quality high-purity refractory powders. According to the specific gravity of the product, it is a lightweight mullite product synthesized by adding organic compound fillers, vacuum extrusion molding, and high-temperature sintering. It is suitable for the hot surface lining and backing of various industrial furnaces in metallurgy, petrochemical, building materials, ceramics, machinery, and other industries. It has the advantages of low thermal conductivity, low heat capacity, high purity, and low impurity content.

(2) Thermal insulation cotton

The thermal insulation cotton is white in color and regular in size. It integrates the functions of fire resistance, heat insulation, and heat preservation, and does not contain any binder. It can maintain good tensile strength, toughness, and fiber structure when used in a neutral and oxidizing atmosphere. The product has low heat capacity, low thermal conductivity, excellent thermal stability, no chalking within the use temperature, and excellent sound absorption and heat insulation properties. It is suitable for industrial kiln wall lining, backing material, high-temperature pipe insulation, kiln masonry expansion joint, furnace door, etc.

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(3) Ceramic fiber module

The ceramic fiber module is made of a ceramic fiber needle-punched blanket of corresponding material and processed on a special machine according to the structure and size of the fiber component. Its elasticity can compensate for the deformation of the furnace shell so that there is no gap between the components. The elastic fiber blanket can resist mechanical external forces. Because of its lightweight, it has less heat storage when used as a thermal insulation material, and low thermal conductivity brings a high energy-saving effect and has the ability to resist thermal shock.

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(4) Corundum heat storage refractory ball

Refractory balls are made of industrial alumina and refractory kaolin as main raw materials through scientific formula, forming, and high-temperature calcination. Mainly play the role of heat storage. The air volume entering the regenerator passes through the heat transfer of the regenerator, and the temperature rises sharply to hundreds of degrees or even thousands of degrees. The spherical heat storage body has the advantages of good thermal shock stability, large heat storage, high strength, easy cleaning, and reusability.

Rongsheng Refractory Materials for Sale for Ceramic Kilns

Rongsheng is an experienced refractory material manufacturer and sales company. Rongsheng’s refractory products have been sold to more than 60 countries around the world, for example, Russia, South Africa, Kazakhstan, Philippines, Chile, Malaysia, Uzbekistan, Indonesia, Vietnam, Kuwait, Turkey, Zambia, Peru, Mexico, Qatar, etc. To purchase high-quality refractory materials for ceramic kilns, please choose Rongsheng refractory manufacturers. Because the refractory lining materials are purchased directly from refractory manufacturers, the price is cheap and the quality is guaranteed. The refractory manufacturers with guaranteed strength in the company can also guarantee the after-sales service of their products. Rongsheng sells refractory materials for ceramic kilns, and we look forward to cooperating with you.

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Mar 13 2021

The Differences in Performance between Lightweight and Heavy Alkali-Resistant Castables

Castable refractory materials that can resist the corrosion of alkali metal oxides (such as K2O and Na2O) at medium and high temperatures are called alkali-resistant refractory castables. The composition of this type of castable is similar to the castable combined with ordinary calcium aluminate cement. It is a mixture composed of alkali-resistant refractory aggregates and powders, binders, and additives. Rongsheng refractory manufacturers will start with the classification of alkali-resistant refractory castables and show you the differences in performance between lightweight and heavy alkali-resistant castables.

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Classification of the Alkali-Resistant Castables

According to the use environment and conditions, alkali-resistant refractory castables are divided into lightweight and heavyweight (also called the dense castable). Those with porosity greater than 45% are lightweight alkali-resistant castables, and those with porosity less than 45% are heavy alkali-resistant castables. The heavy ones can be divided into medium-temperature alkali-resistant castables and high-temperature alkali-resistant castables.

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Lightweight alkali-resistant refractory castable

The aggregates used in the lightweight alkali-resistant refractory castables include alkali-resistant ceramsite, clay porous clinker, waste porcelain, high-strength expanded perlite, etc., and the binder is calcium aluminate cement or water glass. High-silica refractory materials can be used as alkali-resistant materials. This type of material will react with alkali metal oxides to form a high-viscosity liquid phase at high temperatures to form a shafted dense protective layer to prevent further penetration and erosion of the alkali metal melt. Its chemical composition is generally: Al O 30%~55%, SiO 25%~45%. The traditional alkali-resistant castable cement dosage is 25%~30%, and the amount of water added is 20%~25%. Due to the destruction of the cement glue structure at medium temperature (800~1000℃), the strength is greatly reduced, which is only about 50% of the drying strength. Therefore, it is possible to introduce ultra-fine powder and suitable dispersant, the amount of cement is reduced to 10%-20%, and the amount of water added is reduced to 15%-20%.

The physical properties of typical low cement lightweight alkali-resistant refractory castables are as follows:

The temperature is 110℃, 16h drying, the bulk density is 1.5~1.6g/cm3, the flexural strength is 3~6MPa, and the compressive strength is 30~40MPa.
After firing at a temperature of 1100°C for 3 hours, the bulk density is 1.4~1.5g/cm3, the flexural strength is 6.0~6.5MPa, the compressive strength is 40~45MPa, and the linear change rate after firing is -0.3%~-0.5%.
The temperature is 350℃, and the thermal conductivity is 0.4~0.5W/(m·K).

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Heavy alkali-resistant refractory castable

The aggregates used in heavy alkali-resistant refractory castables include bauxite clinker, clay clinker, etc. The binder and alkali-resistant powder are the same as the light alkali-resistant castables. Its main chemical composition is Al O 35%~60%, SiO 35%~60%. The traditional heavy alkali-resistant refractory castable cement uses 20% of the material, and the amount of water added is 10% to 15%. Low cement type heavy alkali-resistant refractory castable cement content is 5%~15%, and water content is 6.5%~7.5%. Low cement heavy alkali-resistant refractory castable binder adopts calcium aluminate cement and silica powder (silica soot). The addition of silica micro powder not only helps to improve the medium temperature bonding strength of the castable but also helps to form an impermeable shaft layer on the surface of the castable lining during use. Its characteristic is that the strength after firing at medium temperature (1000~1200°C) is equivalent to that after drying (110°C), and the alkali corrosion resistance is good.

The physical indicators of typical low cement heavy alkali-resistant refractory castables are as follows:

The temperature is 110℃, 16h drying, the bulk density is 2.20~2.59g/cm3, the flexural strength is 4~8MPa, and the compressive strength is 40~60MPa.
After firing at a temperature of 1100℃ and 3h, the bulk density is 2.20~2.40g/cm3, the flexural strength is 6~10MPa, and the compressive strength is 35~55MPa. The linear change rate after burning is -0.3%~-0.4%, and the thermal shock stability (1100℃ water cooling) is greater than 20 times.
The temperature is 350℃, and the thermal conductivity is 1.2~1.3W/(m·K).

What are the main raw materials used in alkali-resistant castables?

The aggregates used for heavy alkali-resistant refractory castables include clay clinker and waste porcelain materials. The binder and alkali-resistant powder are the same as the lightweight alkali-resistant castable. The binder generally uses calcium aluminate cement.

What is the alkali resistance mechanism of alkali-resistant castables?

The alkali-resistant mechanism of alkali-resistant castables is that they will react with alkali metal oxides at high temperatures to form a high-viscosity liquid phase to form a glazed protective layer to prevent penetration and erosion of alkali metal melts.

What are the suitable furnace parts for alkali-resistant castables?

Heavy alkali-resistant castables are mainly used in the kiln tail, kiln head, preheater, discharge port, tuyere, and other parts of the roasting alumina rotary kiln and cement rotary kiln. Lightweight alkali-resistant refractory castables are mainly used for the preheater top cover, cylinder body, and kiln insulation lining of the above-mentioned rotary kiln. Alkali-resistant castables can also be used in industrial kilns with alkali corrosion in steel, non-ferrous, glass, machinery, petrochemical, and other industries.

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Rongsheng refractory castable manufacturer has rich experience in production and sales. Rongsheng has an environmentally-friendly, advanced, and fully automatic monolithic refractory materials production line with an annual output of 80,000 tons. Our unshaped refractory materials mainly include various types of conventional refractory castables, refractory plastics, refractory ramming materials, as well as various wear-resistant castables, wear-resistant ramming materials, and wear-resistant plastics. They serve the refractory lining of thermal furnaces with their own unique advantages. Whether it is in emergency hot repair, or you need to shorten the furnace repair period, or you need to customize monolithic refractories with special needs, we can provide you with monolithic refractory materials products that best suit your production needs. To learn more about Rongsheng’s unshaped refractory products, please leave your specific needs on our website page, and we will provide you with services according to your specific needs.

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Feb 25 2021

What is the Difference with High Alumina Bricks?

As we all know, there are many types of high alumina bricks with different performances and wide applications. So, among the many types of high alumina bricks, I believe you will have the same doubts as me. With so many high alumina bricks, how are they different from ordinary high alumina bricks? As a refractory manufacturer, we have obtained a convincing answer through testing the original ratio of the product and the performance of the finished high alumina brick. And more and more high-performance high-alumina refractory brick products are used by customers, and the use effect is good. Rongsheng refractories manufacturers kindly remind that not good refractory bricks are suitable for all refractory linings. The choice of refractory lining material needs to be selected according to the specific operating conditions of the thermal furnace equipment. Only in this way can production costs be saved to the utmost extent and economic benefits can be improved. Next, let’s understand the difference between the following refractory bricks and high alumina bricks.

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The difference between low porosity high alumina brick and high alumina brick

The biggest difference between low-porosity high-alumina bricks and high-alumina bricks is the low porosity.

Generally, high alumina bricks are divided into one, two, and three grades, and various grades of high alumina bricks are produced according to different indicators. The zirconium component is an anti-stripping high alumina brick, and the low porosity high alumina brick is a special high alumina brick with low porosity and good thermal shock. Generally, the pores of high alumina bricks are about 22-24%, and the pores of low-porosity Qiao alumina bricks are lower than 18%-19%. The reason for the slight difference in pores is mainly due to the small difference between machines with different pressures during high-pressure molding, but the thermal shock is the same.

Low-porosity high-alumina bricks and general high-alumina bricks also differ in firing time and humidity. Generally, the firing time of high alumina bricks is 60-70 minutes, while the firing time of low porosity high alumina bricks is more than 80 minutes. In this way, the load softening temperature of the two high alumina bricks is also different. Because low-porosity high-alumina bricks need to be added with specific matrix materials, the firing temperature is also higher than that of general high-alumina bricks, so the compressive strength is also different.

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Generally, high alumina bricks have low-temperature requirements, and some waste high alumina bricks are added in a small proportion. So there is also a big difference in production costs.

Low-porosity high-alumina bricks are used in special kiln linings, and the corrosion of the atmosphere in the kiln also requires high-alumina bricks. Therefore, low-porosity and high-alumina bricks not only have low pores, wear resistance, and fatigue resistance, but also have good corrosion resistance. But the price will be relatively high compared with the general high alumina brick.

In short, there is a difference in the internal quality of general high alumina bricks and low porosity high alumina bricks. It can be used according to different situations.

What is the difference between andalusite mullite brick and andalusite high alumina brick?

Andalusite mullite bricks and andalusite high alumina bricks each have their own advantages. Although the main components of mullite brick and high alumina brick have alumina content, the crystal phase of the two is different.

Mullite Brick vs High Alumina Brick — Andalusite Mullite Brick vs Andalusite High Alumina Brick

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When andalusite is heated to 1300°C, it will become mullite, which has the characteristics of resistance to rapid cooling, strong impact resistance, and high load conversion point. During the conversion process of mullite itself, the thermal expansion is low and the crystal is relatively coarse. Andalusite does not need to be calcined and can be directly added to fired or unfired mullite bricks and high alumina bricks. Andalusite has the advantage of creep resistance. During use, impurities will cause the refractory bricks to soften prematurely and have a great influence on creep. Therefore, add a certain proportion of andalusite to mullite bricks or high alumina bricks. Make it resistant to high temperature and rapid cold and heat.

Andalusite high alumina bricks are made of andalusite as the main raw material, added with bauxite, formed by high pressure, dried, and fired at 1500℃. Andalusite high-alumina bricks are characterized by high-temperature resistance, the high softening temperature under load, low creep rate under high temperature, and unavailable volume, high-temperature volume stability, low thermal expansion coefficient during use, and low thermal conductivity. Andalusite has refractoriness of 1830℃ and chemical resistance. Adding andalusite to high-alumina refractory bricks can make the high-alumina bricks have abrasion resistance, higher load softening temperature, and better resistance to rapid cold and heat. The brick joints can be compacted at high temperatures, and the overall density of high alumina brick masonry can be improved, thereby improving the slag penetration resistance.

Andalusite mullite brick is a refractory brick made by adding different proportions of andalusite and mullite. This kind of brick has the advantages of good oxidation resistance, strong fire resistance, high compressive strength, low specific gravity, good peeling resistance, high flexural strength at high temperature, and long service life.

In short, andalusite mullite and andalusite high alumina bricks have similarities and differences. Andalusite mullite bricks are more expensive than andalusite high alumina bricks, and andalusite high alumina bricks are highly resistant to corrosion at high temperatures. Andalusite mullite bricks have good flexibility and stronger peel resistance.

High alumina refractory brick sales

Rongsheng high alumina refractory brick sales, Rongsheng is a refractory brick manufacturer with rich production and sales experience. Rongsheng’s refractory brick products have been sold to more than 60 countries around the world. The product quality is excellent, and the customer acceptance and recognition are high. The ability to support Rongsheng along the way is inseparable from the strength of the Rongsheng refractory factory. The Rongsheng refractory brick workshop is equipped with an advanced refractory brick production line. Various advanced equipment provides a reliable guarantee for high-quality refractory bricks. At the same time, Rongsheng manufacturers strictly control the quality of their products. The purpose is to provide customers with refractory brick products suitable for their production needs. To buy high-quality high-alumina bricks, please choose Rongsheng.

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Feb 4 2021

What Kind of Light Acid-Resistant Castable is Used for Chimney?

The traditional way of lining the chimney is to use acid-resistant cement to build acid-resistant bricks. However, in the masonry mode of acid-resistant brick masonry, the horizontal and vertical joints of the brick are full, which will make the airtightness of the masonry poor. In addition, the dampness of the thermal insulation castable of the thermal insulation layer will cause the thermal insulation performance to decrease. The damage of the heat-insulating castable and the imperfect combination of bricks and bricks will cause corrosive smoke to penetrate the masonry and the insulation layer and corrode the outer cylinder wall. Therefore, the use of lightweight acid-resistant castables for integral casting has also accounted for a certain proportion.

Lightweight Acid-Resistant Castable For Power Plant Chimney

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Masonry of the Inner Wall Lining of the Chimney

It is very inconvenient to construct the chimney with the method of heat insulation castable and lined bricks. Practical problems such as the setting of heat-insulating castables, the treatment of the gaps between the bricks, and the moisture-proof measures, have seriously affected the service life of the chimney.

If the thermal insulation castable and the lining of the anticorrosive brick masonry are combined into one. Lightweight or ultra-lightweight acid-resistant castables with strong corrosion resistance, good heat insulation, and high strength are used to make light acid-resistant castable linings by casting. Thermal insulation and corrosion resistance are combined into one, and the overall airtightness has been greatly improved.

Due to the sulfur dioxide in the flue gas in the chimney, there is water in the flue and chimney to form dilute sulfuric acid, and the acid will corrode the acid-resistant castable. Aluminate cement cannot be used as a binder for light acid-resistant castables. Acidic cement will crack and break the lining castables. Therefore, the acid-resistant castable for the chimney lining needs water glass as the binder and aluminate as the cementing agent, which is severely damaged under the action of sulfuric acid.

Acid-resistant Castable for Chimney Inner Wall Lining

Lightweight acid-resistant castables are mainly composed of raw materials and curing agents. The curing agent adopts ammonium phosphate or ammonium chloride or sodium fluorosilicate, which shall not be crushed and used. After stirring, the light acid-resistant castable with a specific gravity of 0.8-1.0. The initial curing time of the light acid-resistant castable is 40 minutes. It is poured into the template and formed in 2 hours. After 24 hours, it is demoulded and then dried naturally. Because the lightweight acid-resistant castable has good sulfuric acid corrosion resistance, it can fully meet the anti-corrosion requirements of the chimney for lining materials.

The light acid-resistant castable is cast as a whole, which can make the lining integrated and airtight, and has a light volume, and also reduces the weight pressure of the chimney.

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Advantages of Acid-Resistant Castable

Acid-resistant castables have good strength and stability when immersed in acid. Generally, the compressive strength increases as the immersion time increases. The advantages of acid-resistant castables are as follows.

Good heat resistance. Lining in the titanium dioxide rotary kiln, the service temperature is as high as 950℃-1000℃.
The acid-resistant castable has stable performance in various concentrations of organic acid and inorganic acid, especially in dilute acid, industrial water, and neutral aqueous solution without crystal salt. Has high impermeability.
Acid-resistant castable adopts a non-toxic curing agent, which is non-toxic to operators and construction personnel. Approved by the medical and health department, it can be used in anti-corrosion engineering of food, medicine, and other equipment.
Curing at room temperature, simple construction, convenient use, easy to transport, and moisture-proof storage. Compared with organic acid-resistant materials, acid-resistant castables are inexpensive. In addition to having the same properties as organic acid and corrosion resistance, it also has the unique performance of resistance to strong oxidizing media.

Acid-resistant castables are suitable for the lining of petrochemical and corrosive equipment. It can fully resist the erosion of acid gases and solutions and is widely used in equipment such as steel chimney lining, flue sulfuric acid tank lining, blast furnace hot blast stove top protective layer, and other equipment.

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Rongsheng Acid-resistant Castable Manufacturer

Purchase high-quality acid-resistant castables for chimneys from Rongsheng refractory manufacturers. Rongsheng’s advanced environment-friendly and fully automatic unshaped refractory production line have an annual output of tons. If you need to buy various unshaped refractory lining materials, please contact us. We will provide you with high-quality refractory castable products suitable for your production needs according to your specific needs.

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Jan 9 2021

The Influence of Certain Oxides on the Performance of Magnesia Chrome Bricks

In the production process of magnesia chrome bricks, there will be a variety of additives. For example, chromium oxide, aluminum oxide, zirconium oxide, iron oxide, etc. These additives have a very important influence on the performance of magnesia chrome bricks. The Rongsheng refractory manufacturer will make the following specific analysis on the influence of these four oxides on magnesia-chrome bricks.

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The Influence of Chromium Oxide on Magnesia Chrome Refractories

Chromium oxide is one of the main components of magnesia-chromium refractories. Appropriate addition of chromium oxide components with high purity and small particle size to magnesia-chromium refractories has the following three main effects on magnesia-chromium refractories.

(1) Increase the direct binding rate

When the content of Cr203 in periclase increases, the dihedral angle between silicate melt and periclase increases. This principle also leads to poor wettability between silicate and magnesia-chromium spinel compared to silicate and magnesia-iron spinel. This phenomenon also causes the silicate to be distributed only in the form of islands between the magnesia-chromium spinels, and the direct bonding in the magnesia chrome bricks body increases.

(2) Improve strength

During the sintering process, the periclase solid solution in the magnesia-chromium refractory material has the dissolution and re-dissolution of spinel during the re-dissolution of silicate. Because of their similar crystal structure, spinel can form a large amount of secondary spinel around the periclase crystal, which improves the strength of the product and the slag resistance. The addition of high-purity small particles of chromium oxide to the magnesia chrome brick can promote the formation of spinel and promote the formation of secondary spinel.

(3) Increase slag viscosity

When the magnesia-chromium refractory contains more chromium oxide components, due to the low chemical activity of the chromium oxide components when chromium oxide is present in the slag, the viscosity of the slag component increases.

The Influence of Alumina on Magnesia Chrome Refractory Bricks

The addition of alumina to magnesia chrome refractory bricks has different effects depending on the raw materials used. The raw materials contain more impurity components such as CaO and SiO2. The addition of appropriate alumina components can promote the sintering of magnesia chrome refractory bricks, and the brick structure will become denser. This is because alumina can form low-melting substances with calcium silicon and other components in the refractory bricks. The formation of these low-melting substances accelerates the sintering and densification process.

However, due to the different content of CaO and SiO2 in the raw materials, the influence of the crystal structure of periclase and other crystalline materials in the raw materials causes differences in the content and diffusion of CaO and SiO2 in the brick body. When the amount of CaO and SiO2 diffused to the boundary is not enough to meet the reaction rate of alumina, the remaining alumina will react with MgO in the periclase crystals. The reaction equation is as follows:

MgO+Al2O3=MgO·Al2O3

That is, spinel is generated at the grain boundary and other positions in the brick body, and the volume and density of the magnesia-aluminum spinel, which is the reaction product of MgO and Al2O3, is quite different. Therefore, this reaction is accompanied by a larger volume expansion. This hinders the sintering reaction of the magnesia-chrome brick body to a large extent, which increases the pores in the brick body and reduces the strength.

In other words, to add alumina to the magnesia-chromium refractory bricks, it is necessary to consider the CaO and SiO2 components in the raw material, and appropriately add alumina. If most of Al2O3 is added, it can react with the silicon-calcium component in the brick body to form a low melting phase, and it can present a continuous distribution in the brick body. At this time, due to the increase in the amount of liquid phase during the sintering process, it can promote the material transfer during the sintering process, promote the sintering of the brick body, and increase the density of the product. On the contrary, if the content of CaO and SiO2 is too low, it is not enough to meet the conditions of consuming Al2O3 to generate the liquid phase. Because the Al2O3 at this time will react with the MgO component in the brick body to form a spinel. The volume expansion caused by the formation of spinel cannot be well alleviated, the density of magnesia chrome bricks products will be reduced, and the compressive strength at room temperature will be affected.

The Influence of Zirconia on Magnesia-Chromium Refractory Materials

The addition of zirconia can improve the performance of magnesia-chromium refractory materials to a certain extent.

(1) ZrO2 has strong chemical stability. It shows good chemical inertness to general glass melts and acids and bases and is not easy to be wetted by metal solutions.

(2) ZrO2 can change the aggregation state and grain shape of the crystal grain boundary phases in the magnesia-chrome refractory materials, and reduce the dihedral angle between the crystals, and promote the bonding between the crystals.

However, the addition of too much ZrO2 is detrimental to magnesia chrome refractory materials. This is because ZrO2 has a small solid solubility in magnesium oxide. If an excessive amount of ZrO2 is added, the residual ZrO2 will remain between the crystal grains, hindering the mass transfer during sintering, and is not conducive to the densification of the brick body.

The Influence of Iron Oxide on Magnesia Chrome Bricks

Due to the presence of magnesia-iron spinel, iron oxide can promote the sintering of magnesia chrome bricks to a certain extent. However, due to the valence of iron oxides, the solid solubility of the two oxides FeO and Fe2O3 in periclase is slightly different. For this reason, magnesium-chromium products with high iron oxide content are not suitable for copper smelting production with an unstable atmosphere and unstable temperature.

If a magnesia chrome brick with higher iron content is used in a copper converter, it may generate a bulging and loose layer due to the following phenomena. In the case of high-temperature reduction, Fe2O3 in the periclase solid solution will be reduced to FeO and low-iron spinel in the brick body. In the lower temperature or oxidizing atmosphere, the low-iron spinel will be oxidized again to generate MgOFe2O3. In this process, the volume changes, which will cause the explosion of magnesia chrome refractory and the formation of evacuation layers.

Rongsheng Magnesia Chrome Brick for Non-Ferrous Smelting

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The above-mentioned substances have not only their own influence on magnesia chrome refractory materials during the use of the copper smelting process. Its interaction with iron-silicon slag and SO2 atmosphere is also worth noting.

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Yearly Archives: 2021

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Two Different Types of Low Cement Castable Composition

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Classification of the Alkali-Resistant Castables

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Rongsheng Refractory Castables Manufacturer

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The difference between low porosity high alumina brick and high alumina brick

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What is the difference between andalusite mullite brick and andalusite high alumina brick?

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High alumina refractory brick sales

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Masonry of the Inner Wall Lining of the Chimney

Acid-resistant Castable for Chimney Inner Wall Lining

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Advantages of Acid-Resistant Castable

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Rongsheng Acid-resistant Castable Manufacturer

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The Influence of Chromium Oxide on Magnesia Chrome Refractories

The Influence of Alumina on Magnesia Chrome Refractory Bricks

The Influence of Zirconia on Magnesia-Chromium Refractory Materials

The Influence of Iron Oxide on Magnesia Chrome Bricks

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