Aluminum-Magnesium Castables Combination Methods

 Aluminum-magnesium castable is a refractory castable with bauxite and magnesium oxide as its main components. It is widely used in the industrial practice of out-of-furnace refining and ladle refractory materials. The MgO can be added in the form of magnesia or pre-synthesized spinel. Aluminum-magnesium castables can be divided into different types. According to different raw materials, it is divided into high-purity corundum-spinel castables and low-purity bauxite-spinel castables. According to the different ways of introducing spinel, it can be divided into aluminum-spinel castable (Al2O3-MA castable) and aluminum-magnesium castable (Al2O3-MgO castable). According to the bonding method, it can be divided into cement-bonded, hydrated bonded, silica powder bonded, magnesium silicon water bonded, and other castables.

Aluminum-Magnesium Castables

How to Combine Aluminum-Magnesium Castables

Binders are also an important component of aluminum-magnesium castables. The bonding methods used in aluminum-magnesium castables are generally calcium aluminate cement bonding, silica powder bonding, hydrated alumina bonding, sol bonding, magnesium silicon water bonding, etc.

(a) Cement bonding

In the early stages of the development of aluminum-magnesium castables, pure calcium aluminate cement was used for bonding. This is because cement calcium aluminate reacts with Al2O3 in the matrix to form CA6, which is a highly refractory phase. However, as the amount of cement added increases, the fluidity of the castable decreases. At the same time, due to excessive CaO content at high temperatures, it will react with SiO2, Al2O3, and MgO in the matrix to form a low melting phase. As a result, the high-temperature performance of the castable is reduced. Zhang Wenjie et al. studied the effect of the amount of water added to cement on the thermal expansion behavior of aluminum-magnesium castables after high-temperature firing. The results show that as the amount of cement added increases, the CA2 and CA6 phases in the sample increase, and the linear change rate of the sample after high-temperature heat treatment increases. Gu Huazhi et al. studied the effects of silica powder, magnesia, and cement on the properties of high-purity aluminum-magnesium castables. Studies have pointed out that pure calcium aluminate cement and Al2O3 fine powder in the matrix begin to react at about 1000°C, and the reaction generates CA2 and CA6. The reaction is accompanied by volume expansion, which can reduce the strength ratio after high-to-medium temperature firing and also contribute to the improvement of the high-temperature performance of the sample.

(b)MgO-SiO2-H2O combination

There are many studies on MgO-SiO2-H2O bonding and condensation bonding. The combination of MgO-SiO2-H2O is used in aluminum-magnesium castables. On the one hand, due to the polymerization of SiO2 gel formed by the interaction between SiO2 powder and water, the amount of water added is reduced and the fluidity of the castables is greatly improved. On the other hand, the combination of MgO-SiO2-H2O can inhibit magnesia hydration. However, if too much silica powder is added, it will form a low melting point 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.

What is Lightweight Insulating Refractory Castable - RS Refractory Materials Manufacturer

 Lightweight castables are lightweight, have low thermal conductivity, are easy to use, and are cheap. Lightweight castables are also continuously developed according to the different needs of the market. Composite lightweight refractory castables are continuously developed to meet the use of furnace linings.

What is Lightweight Insulating Refractory Castable?

Lightweight Insulating Refractory Castable is a refractory castable with lightweight, high strength, and excellent thermal insulation properties. It is mainly composed of lightweight aggregates (such as perlite, vermiculite, etc.), high-temperature stable materials, binders, and additives.

lightweight insulating refractory castable

Introduction to Lightweight Insulating Refractory Castables

Lightweight insulating refractory castables have many advantages, such as low thermal conductivity, low heat capacity, good thermal insulation properties, earthquake resistance, impact resistance, erosion resistance, etc. It is widely used in various high-temperature industrial equipment, such as industrial furnaces, heat treatment furnaces, steel furnaces, glass melting furnaces, etc. To improve the energy efficiency of equipment and reduce energy consumption.

According to the material composition and performance characteristics of lightweight insulating refractory castables, they can be divided into different types. Such as perlite lightweight heat-insulating refractory castables, vermiculite lightweight heat-insulating refractory castables, high-aluminum lightweight heat-insulating refractory castables, etc. Each type of lightweight insulating refractory castable has its own unique characteristics and scope of application, and users should choose according to specific circumstances.

When using lightweight insulating refractory castables, you need to pay attention to the following points:

The mixing ratio. The mixing ratio of lightweight insulating refractory castables should be in accordance with the instructions for use. Different types of lightweight insulating refractory castables have different mixing ratios, and users should choose according to specific conditions.

Construction method. The construction method of lightweight insulating refractory castables can be selected according to specific conditions, and methods such as manual construction, mechanical construction, and pumping construction can usually be used. Different construction methods will affect the density and uniformity of castables.

maintenance. Lightweight heat-insulating refractory castables should be kept moist during the curing period, and the curing time is generally more than 24 hours. During the curing period, it is necessary to prevent the castable from drying out prematurely and causing cracking.

lightweight high-strength insulating refractory castable

Lightweight Refractory Castables with a Bulk Density of Less than 1.5g/cm3

Refractory castables with a bulk density of less than 1.5g/cm3 are lightweight refractory castables. Lightweight refractory castables mainly play the role of thermal insulation. Refractory castables with a bulk density greater than 1.5g/cm3 and less than 1.8g/cm3 can be called semi-lightweight castables. Castables greater than 1.8 are heavy castables.

The raw materials of lightweight castables are lightweight aggregates and powders added in proportion, and the binding agent is also combined with high alumina cement. There is also a combination of water glass and phosphoric acid. However, the amount of binder added to lightweight castables is large, and the proportion of water added during construction is also larger than that of heavy castables.

The characteristics of lightweight castables are low density, lightweight, low thermal conductivity, and good heat insulation effect. There are many varieties of lightweight castables, and their properties can be divided into neutral and acidic.

Application of Lightweight Refractory Castables in Kiln Linings

The lining of the kiln is basically equipped with a heat insulation layer. The lightweight castable used in the heat insulation layer cannot directly contact the flame. The outer layer of the insulation layer usually has castables or refractory bricks for the working layer. Lightweight refractory castable has a good heat insulation effect, slow heat dissipation, and a good heat preservation effect. And it (http://www.aluminabricks.com/refractory-castable/lightweight-refractory-castable/) can save the fuel used by the kiln. In different kiln linings, different lightweight castables or lightweight castables with different properties are used.

Some high-grade lightweight refractory castables can also be used as the working layer in the furnace lining. For example, acidic acid-resistant lightweight castables with a specific gravity of 1.5 can be used in chimneys or flues, and the effect is quite good. Using this lightweight castable will make the chimney lighter and reduce stress. There is also an alumina hollow ball refractory castable, which is a high-end material among lightweight castables. Can be used within special lightweight kiln linings that are not only high-temperature resistant but also lightweight.

To purchase high-quality lightweight refractory castables, please choose Rongsheng Refractory Materials Manufacturer. We can provide you with comprehensive refractory lining material services and good customer service to ensure long life and efficient operation of high-temperature industrial furnace linings.

Precautions for Using Ladles

When the ladle is used for the first time, all parts of the ladle must be thoroughly inspected. Parts such as gantry hooks, various protective devices, and safety forks should be inspected in particular detail. If damage is found, it should be replaced in time. The steel ladle must be inspected with 2 times the load during initial use.

Precautions for Using Ladles

Precautions Before Using the Ladle

Repair of ladle lining. Refractory materials, including refractory bricks, refractory mortar, and refractory mud, should be appropriately selected according to the type of molten steel. For example, ordinary carbon steel uses silicon refractory materials; ordinary alloy steel uses aluminum refractory materials; manganese steel uses magnesium refractory materials.

When using a plug-rod ladle, the ladle nozzle and refractory layer must be constructed in the following order.

(1) Install the sprue brick at the nozzle at the bottom of the package. The sprue brick should be paired with the plug brick and ground before installation.

(2) Install the seat brick.

(3) Use refractory bricks to build the bottom and walls of the ladle. The bottom part of the bag should be sloped 1/20 towards the water outlet. For the used package body, if the corrosion of the refractory layer is not large, you can only replace the refractory bricks at the nozzle and repair part of the refractory layer.

Refractory Bricks for Steel Ladle

(4) Before using the plug rod, the resistant material must be constructed in the following order. Insert the stopper rod through the ground stopper brick and secure it in place. Place the sleeve brick on the plug rod, and fill the space between the sleeve brick hole and the plug rod with dry fine sand or asbestos powder. The contact surfaces of plug head bricks and sleeve bricks should be coated with refractory mud. Add a pressure cap to the end of the sleeve brick, and use a nut to tighten the sleeve brick through the gland.

Installation of sliding spouts. First, install the sliding nozzle well bricks, and then build the refractory material according to the specified thickness of the refractory material.

Ladle baking

Install the plug rod filled with refractory material on the cross arm. During installation, the concentricity of the plug brick and the sprue brick must be adjusted to ensure sealing. After the adjustment is completed, use nuts to reliably fix the plug rod and the transverse hip.

After assembly, the newly repaired refractory ladle should be thoroughly baked 6 hours before use. The baking temperature should be gradually increased from low to high (800℃, constant temperature for 1 hour).

Lower the hanger while the ladle is baking. The drying bag can be used with gas or natural gas. The baking time of used ladles can be shortened. However, the baking time should not be less than 2 hours, and the baking temperature should not be lower than 800℃.

Precautions for Casting Use

1. Before casting, first check whether the safety fork is reliable.

2. Align the pouring opening of the pouring ladle with the opening of the pouring cup of the mold.

3. Before pouring, use the lever to press the plug rod and loosen the locking bolt at the same time to make the pouring ladle in the poured state. When pouring, slowly lift the plug rod, and the molten metal will flow out from the bottom nozzle. The greater the lifting distance of the stopper rod, the greater the flow rate of molten metal. Therefore, the pouring speed can be controlled using a lever.

4. After pouring, check whether the sprue bricks, plug bricks, and sleeve bricks at the nozzle are severely corroded, cracked, or otherwise damaged. If it is damaged, it should be replaced. If it is not damaged, the adhered metal residue or other adherents should be cleaned and maintained for use. Under normal circumstances, the sprue bricks, plug bricks, and sleeve bricks need to be replaced after one package of molten steel.

5. When using the sliding nozzle ladle, pay attention to the drainage sand in the nozzle. When pouring a casting, first open the sliding nozzle mechanism to release a portion of the molten steel (release the drainage sand). Prevent the drainage sand from rushing into the casting and affecting the quality of the casting.

After the ladle is used, the bad refractory materials should be removed and the refractory materials should be rebuilt. At the same time, inspect the pouring ladle, including hoists, lifting rings, beams, safety devices, stopper rods stopper rod driving devices, and sliding nozzle devices.

Acid-Resistant Castables for Lining of Acid-Resistant Chimneys and Liquid Sulfur Pools

Acid-resistant castables are divided into heavy, semi-light, and light. Their main function is to be used for furnace linings that resist acid erosion. Acid-resistant castables are generally combined with acid-resistant cement and are applicable to acid-resistant chimneys and liquid sulfur pool linings in the petrochemical industry.

Acid-Resistant Castables for Lining of Acid-Resistant Chimneys

The acid-resistant castable for acid-resistant chimneys is similar to and different from other refractory castables. It belongs to an acidic medium. During production, the raw materials are also processed into granules and fine powder in an acidic medium, and a certain proportion of ultra-fine powder and additives are added. However, the acid-resistant castable used for lining the liquid sulfur pool cannot be used in atmospheres with large temperature differences, nor can it be used in construction in places that are too humid. If the temperature is not suitable, it will reduce the later use strength and acid resistance of the acid-resistant castable, and it will peel off.

Application of acid-resistant castables

Chimneys are made of acid-resistant castables, generally semi-lightweight. It can not only be used for thermal insulation but also be resistant to erosion and acid gas erosion. Because semi-lightweight acid-resistant castables can save energy and improve the operation rate and service life of the chimney. At the same time, the weight of the chimney body is not too heavy.

Application of acid-resistant castables

Acid-resistant refractory castables are all used in furnace linings that resist acidic atmospheres and cannot be used in neutral or alkaline furnace-lining atmospheres. Due to the high-temperature resistance of acid-resistant castables, it is not as good as high-aluminum series castables used in neutral atmospheres. In an alkaline atmosphere, use castables inferior to the magnesium series. It is mainly used in acidic atmosphere chimneys, flues, nitric acid shrink tower linings, and acid gas container linings. The high-temperature resistance of acidic refractory castables is not as good as that of the high aluminum series and magnesium series.

However, acid-resistant castables can be used as separate lining materials. When used in a furnace with a consistent atmosphere, the castable's own acid resistance will be exerted, and it cannot be used as a furnace lining in other atmospheres. First, there is a gap in high-temperature resistance, and then there is a gap in resistance to erosion by other atmospheres.

In other words, acid-resistant castables, whether heavy, semi-light, or light, can only be used as furnace linings for acid gases.

Lightweight acid-resistant castable for anti-corrosion flue

Lightweight acid-resistant castable is mainly used in anti-corrosion flue and chimney linings, acid storage tanks, pickling tank linings, and nitric acid shrinkage tower linings. Acid recovery furnace lining and other refractory castables corroded by acidic high-temperature gases. It can improve the air tightness and integrity of the lining wall and the corrosion resistance of the lining. It is a kind of refractory material that is widely used at present.

Lightweight acid-resistant castable

Characteristics of lightweight acid-resistant castables for chimney lining

1. It has the characteristics of light volume and high compressive strength.

2. It is resistant to acid and acid gas corrosion.

3. It has the characteristics of heat insulation, heat preservation, and low water absorption.

4. It can significantly improve the air tightness, integrity, and anti-corrosion ability of the lining.

Characteristics of lightweight acid-resistant castables for lining pickling tanks

1. Low thermal conductivity. The thermal conductivity of lightweight acid-resistant castable is only 0.12-0.16W/(m·k), which is about 1/10 of ordinary concrete. Therefore, the thermal insulation effect can be better exerted.

2. High temperature resistance. The castable can be used for a long time in a high-temperature environment of 1000°C without cracking or falling off. Excellent fire resistance.

3. Strong corrosion resistance. Lightweight acid-resistant castable has good acid and alkali corrosion resistance. It can be used for a long time in corrosive environments such as strong acids and alkalis without causing damage or destruction.

4. Simple construction. The castable is easy to construct and uses water as a diluent. It can be mixed with water on-site to form a slurry and then poured directly on the surface of the equipment. No special construction equipment or technology is required. The labor intensity and construction difficulty of workers are greatly reduced.

The characteristics of the lightweight acid-resistant castable used for lining the acid recovery furnace enable it to be widely used as a lightweight acid-resistant castable. At the same time, as an unshaped refractory castable, it can also be made into prefabricated parts of various shapes for use. It is a refractory product that is widely used and ideal at present.

What factors should be considered when purchasing circulating fluidized bed furnace lining refractory materials?

The circulating fluidized bed boiler has strong fuel adaptability, good combustion stability, a simple preparation system, and a long service life. Widely used in metallurgy, chemical industry, electric power, construction, and other fields. The normal operation of a circulating fluidized bed boiler is inseparable from the lining with reasonable structure, wear resistance, and fire resistance. How to choose circulating fluidized bed furnace lining refractory materials? What factors should be considered when purchasing circulating fluidized bed furnace lining refractory materials? RS refractory material manufacturer has material supply and construction experience in multiple circulating fluidized bed projects and can provide high-quality refractory castables and other refractory material products for circulating fluidized bed boilers.

RS Refractory Castable Factory

First, determine the use environment and needs, and select suitable refractory materials.

Depending on the kiln type, combustion material, high temperature, acid and alkali properties, and other conditions, the applicable refractory materials are also different. Generally speaking, high-aluminum or corundum products can be selected for neutral environments, and magnesium products can be selected for alkaline environments. When the combustion temperature is around 1,000 degrees, clay products should be selected, between 1,200 and 1,400 degrees, high aluminum products should be selected, at around 1,600 and 1,700 degrees, corundum products should be selected, and above 2,000 degrees, special refractory materials should be selected.

Then, refractory materials are combined and applied according to the use location.

Different refractory materials are suitable for different parts of circulating fluidized bed boilers. The instantaneous temperature of the ignition air duct is high, so it is suitable for materials with high refractoriness and high thermal shock resistance. The temperature of the steering chamber in the dense phase area of the furnace, the furnace outlet, the furnace top, and the superheater is high, and the thermal shock is strong. Suitable for refractory materials with high wear resistance, high thermal conductivity, and low refire line change rate. The temperature at the inlet of the separator is high and the smoke velocity is high. The refractory materials in this part need stronger wear resistance and thermal shock resistance.

Finally, consider cost and performance-to-price ratio and choose affordable refractory materials.

The prices of refractory materials with different qualities and properties vary greatly. When selecting materials, the cost-effectiveness of the materials should be considered, and higher-quality refractory materials should be selected in high-temperature sections, ultra-high-temperature sections, and areas with severe corrosion. In the medium and low-temperature sections and parts that are weakly eroded, more economical and affordable refractory materials can be selected while meeting the needs of the working conditions.

It can be seen that when selecting refractory materials, more comparisons should be made in terms of material type, quality, cost, etc. Then choose a company with strong comprehensive strength.

Rongsheng Refractory Materials Manufacturer is a powerful refractory material manufacturer. Our refractory products have been sold to more than 80 countries and regions around the world. We have multiple production plants, mainly producing refractory bricks for high-temperature industrial furnaces, unshaped refractory materials, refractory prefabricated parts, and other refractory products. We have extensive experience in the batching and construction of refractory products for circulating fluidized bed boilers. To purchase high-quality refractory castables for circulating vulcanized bed boilers, please choose a competent refractory material manufacturer. RS refractory material manufacturer is reliable, has fast delivery, and has comprehensive customer service.

How to Extend the Service Life of Checker Bricks used in Glass Melting Furnaces?

The Checker Brick body is the heat transfer part of the regenerator and the most important component of the regenerator structure. Whether the structure of the Checker Brick body is reasonable not only affects the service life of the regenerator but also directly affects the heat storage efficiency of the regenerator, which in turn affects the thermal efficiency of the entire furnace. Therefore, the refractory materials that make up the lattice body are required to be able to withstand high temperatures, resist corrosion, accumulate a lot of heat, transfer heat quickly, and have good thermal vibration stability. The entire Checker Brick body is required to have good structural stability.

Checker Brick with Good Structural Stability

The regenerator checker brick body that has been exposed to high-temperature flue gas for a long time is subject to periodic cooling and heating and is subject to erosion by flying materials and alkali vapor. The lattice holes can become clogged or damaged, causing the bricks to deform, crack, or even collapse. In the mild case, it will reduce the thermal efficiency of the melting furnace; in serious cases, it will directly affect the production and operation of the melting furnace. Therefore, regular observation and inspection of the Checker Brick is very necessary. The main contents of the inspection are:

① The state of melting, burning, swelling, cracking, and falling off of checker bricks.

② Check whether the Checker Bricks’ holes are blocked. If there is a blockage, the location, scope, and severity of the blockage need to be observed clearly.

③Whether the checker brick body has collapsed.

④ Check the slag accumulation condition in the regenerator and flue.

⑤ Check whether there is any air leakage in the regenerator and flue.

checker brick exposed to high-temp flue gas

Sodium silicate melting production requires stable temperature, kiln pressure, and normal feeding operations. However, it should be noted that regular removal of dust accumulation in the regenerator and flue is a necessary condition for stable operation.

The reversal of the furnace every 20 to 30 minutes changes the direction of the flame flow. While the regenerator checker bricks on one side are heated by high-temperature exhaust gas, cold air enters the regenerator Checker Bricks on the other side, causing the temperature of the Checker Brick to gradually decrease. The temperatures of the regenerator Checker Bricks on both sides show periodic crossovers. Only when the temperature curves of different cycles intersect are basically the same can the temperature be stabilized.

The slag accumulated in the Checker Brick holes should be removed regularly. Cleaning is done on the hot side. If there is a lot of slag accumulated and cannot be completely removed when the fire needs to be changed, the fire should be changed on time and then removed when the fire direction is changed. After removing the slag, a layer of quartz sand should be spread to prevent the dust slag from sticking to the flue pavement tiles.

 

RS Checker Bricks Manufacturer

There are several measures to extend the service life of Checker Bricks:

① The ascending Checker Brick bricks are made of alkaline refractory materials that are resistant to high temperatures and corrosion.

② Widen the furnace bar holes and purge them in time.

③Reasonably control the temperature of the regenerator to avoid excessive kiln pressure.

④ Reasonably arrange regular hot repairs.

⑤ Reduce powder flying.

⑥ Set long fire regularly, or use an oil gun to burn nodules, etc.

Therefore, in order to better extend the service life of the Checker Bricks used in glass melting furnaces, in addition to choosing high-quality refractory bricks when purchasing Checker Bricks. It is also necessary to carry out maintenance and repair during its use, so as to ensure the service life of the checkered bricks. This reduces the number of furnace shutdowns and furnace repairs.

Expansion Joints for Suspending Anchoring Bricks on the Furnace Roof

Anchor bricks are also called hanging bricks. Anchor pieces and anchor bricks are novel and relate to traction bricks or tension bricks for industrial furnaces. Especially when it comes to the anchor bricks used in the industrial furnace roof in the forging industry. The neck part in the middle is where the hanging hook is installed. Make the hook into the shape of a "door" and then align it, clamp the middle of the anchor brick, and hang it on the I-beam. Another way is to anchor the brick with a hanging hole. There is a hole with a diameter of about 20mm at the top of the brick. Then the screw is made into an L shape, one end goes through the hole and then the nut is tightened, and the other end is hung on the I-beam to tighten the nut. In terms of the shape of the current industrial anchor bricks, there are many types, but the ultimate purpose is the same. That is to say, it will be used as the tensile support of the furnace top refractory castable to ensure the firmness and high-strength stability of large-area pouring.

Anchoring Bricks for the Furnace Roof

Expansion joints for suspending and anchoring bricks on the furnace roof

The hanging distance of the anchor bricks in the furnace roof is 400~500mm, 500mm in the horizontal direction, and 400mm in the longitudinal direction. During construction, the inner surface of the castable and the top surface of the anchor brick should be kept on the same vertical plane as possible. The hanging size can also be properly adjusted according to the location of the gravity point. When the furnace roof is hung, it is mostly cast as a whole or rammed with refractory plastic. The form of furnace roof is divided into a flat roof and a vault. The vault is generally made of refractory castables, and the flat roof can be made of refractory plastic. No matter which pouring method is adopted, different expansion joints should be set for the anchor bricks, and they should not be directly dry poured without any expansion joints reserved. The raw materials used in the production of anchor bricks are generally products made of aluminum-silicon materials. At a certain temperature, SiO2 quartz residual crystals will expand to a certain extent. The common way to reserve expansion joints is to apply black asphalt paint on the outer surface of anchor bricks.

Common problems in the use of anchor bricks

The common problem of anchor bricks in use is fracture, and the cause of fracture is directly related to the stress in three aspects. The first is tensile strength, the second is compressive strength, and the third is shear stress. The most common is that in addition to the tensile stress caused by gravity, it also bears a large shear stress during use. Since there is a big difference in temperature between the part of the upper layer that is not embedded with castables and the buried part of the lower layer, the physical expansion after heating is also quite different. There will be a temperature difference in shear force between the layers in use, and the magnitude of the shear force is related to the expansion coefficient of the anchor brick after the temperature difference changes.

Suspending Anchoring Bricks on the Furnace Roof

Considering the anchor brick from the aspect of production: one is the refractoriness, and the other is the tensile strength. Refractoriness is generally not a problem, the most important thing is the tensile strength. We are currently most concerned about the cold tensile strength of bricks. Because the weight of the entire furnace top is suspended at the neck of the upper part of the hanging brick, it is often at a low temperature here. Therefore, as long as the normal temperature strength of the brick is sufficient, no fracture will occur here, and if the normal temperature strength is insufficient, the so-called fracture will occur.

The material of the hanging brick and its strength characteristics at different temperatures, the strength of the sintered refractory product mainly comes from the ceramic bonding between the particles in the refractory material. The higher the degree of this ceramic junction, the higher its strength. The ceramic bonding of high alumina refractory products is mainly the result of liquid phase sintering, that is, the liquid phase is formed in the refractory material at a high temperature to promote the bonding and material migration between particles. The greater the amount of liquid phase formed. The better the sintering strength, the higher the strength in the cold state. However, cold strength and hot strength are often contradictory. Although a large amount of high-temperature liquid phase promotes sintering and high low-temperature strength, when used at high temperatures, this large amount of liquid phase will reappear, and the high-temperature strength will decrease. The higher the amount of high-temperature liquid phase, the lower the high-temperature strength.