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Refractory Castable Materials for Boiler Furnaces

December 16, 2024October 29, 2024 by rsrefractorycastable

The boiler furnace is a three-dimensional space surrounded by furnace walls for fuel combustion. Its function is to ensure that the fuel is burned as much as possible and to cool the flue gas temperature at the furnace outlet to a temperature that allows the convection heating surface to work safely. Rongsheng Refractory Material Manufacturer can provide high-quality boiler furnace refractory materials – refractory lining maintenance services for high-temperature industrial furnaces. Contact Rongsheng for detailed information.

High-Alumina Refractory Castables Manufacturer

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Refractory Castables for Furnace Lining

Common refractory castables for furnace lining include steel fiber, special high aluminum, brown corundum, silicon carbide, mullite, etc. Aggregates and powders made of high-temperature resistant or high-temperature wear-resistant products, with binders, ultrafine powders, and other products added, are mixed and made. They can be cast or made into high-temperature-resistant prefabricated parts and hoisted for construction.

Phosphate Bonded High Alumina Refractory Plastics

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High-Temperature Resistant Plastic Refractory for Furnace Lining

High temperature resistant plastic for furnace High temperature resistant plastic for furnace is basically the same as castable material, but the combination and construction methods are different. It is composed of 80% to 85% high-strength aggregate and fine powder. After adding binder and plasticizer, a small amount of blending agent is added. After sufficient mixing, it is a kind of hard mud paste, which can be made of various high temperature resistant raw materials. It belongs to a more plastic and shape-changing refractory material.

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Ramming Material Refractory for Furnace Lining

Compared with other amorphous refractory materials of the same material, ramming material for furnaces is dry or semi-dry and loose. The dense structure is obtained by strong ramming, and the combination will have density only when it is heated to the sintering temperature. Compared with castables and plastics, it has more reliability and corrosion resistance at high temperatures. However, its service life depends to a large extent on the pre-burning before selection or the sintering amount during the first use. If the heating surface is sintered as a whole without cracks and does not separate from the bottom layer, the service life can be improved.

The refractory materials for furnaces should not only look at the product quality, but also the furnace drying is an important link. The furnace should not only be baked, but also the necessary furnace boiling should be implemented. The heating boiler in winter should also be baked before it is put into operation to drive away the moisture in the furnace body and chimney flue. Boil the furnace means to put scientifically proportioned chemicals into the furnace to dissolve and remove the oil, dirt, rust, etc. attached to the inner wall of the heating surface during the manufacturing or transportation of the boiler, so as to ensure the safe operation of the boiler and the quality of steam and hot water.

Causes of Damage to Refractory Castables for Furnaces and Methods of Repairing Castables

Speaking of the current structure of boilers, it is estimated that a large part of the structure is selected refractory castables. Refractory castables not only have high performance and good performance. In many cases, refractory castables can be modified to produce different properties of refractory materials, which is one of the reasons why refractory castables are very popular now.

However, one of the puzzling problems is that refractory castables are used for a long time, or a considerable part of the products are extremely vulnerable to damage during the curing process. When building boilers, the use of aluminate cement refractory castables is mainly caused by the combination of aluminate cement and castables.

Surface crushing caused by alkaline impurities

In the material, the presence of soluble alkali increases solubility and accelerates the reaction as an important prerequisite. In cement castables, the increase in cement content and the increase in system alkalinity will lead to larger hydrated minerals, which is conducive to the reaction. Curing environment temperature and humidity are important factors for damage. Generally, the greater the humidity, the easier it is to wet the pores in the casting body. Under humid conditions, dissociation is easier and the reaction is smoother. The density of the green body is also an important factor. When the porosity of the green body is high, water in the air is more likely to diffuse into the green body, so that the damage reaction continuously enters the depth of the green body, resulting in casting. The crushing of the table and the inside will damage the material. In addition, the shape and thickness of the blank also affect the progress of the reaction. In addition, the quantity and quality of construction water will also affect the damage.

Surface pulverization caused by carbonation reaction

Surface pulverization caused by carbonation reaction can be divided into two types. One is direct carbonation, where carbon dioxide directly reacts with the hydration products of cement to form a calcium carbonate-calcium aluminate complex. It closes the surface pores and causes surface hardening, thereby inhibiting pulverization. The other is carried out by the catalysis of sodium ions in the presence of soluble alkali metal oxides. This is similar to the mechanism of sodium ion damage, which may lead to the destruction of the castable lining.

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Repair of Furnace Lining Refractory Castables

The damage and repair methods of furnace lining refractory castables are mainly used to solve surface damage.

Wash high-purity raw materials to reduce the content of soluble alkali metals. When preparing refractory castables, choose high-quality refractory aggregates as much as possible, and choose washed and baked raw materials with low alkali content (such as bauxite and corundum). If the raw materials are not calcined (such as andalusite), choose more cautiously and try to use composite sodium and low concentration mixtures. The dispersion effect and filling effect of micropowder are conducive to improving the density of castables. However, when selecting micropowder, the impurity content of micropowder should be properly controlled to minimize the amount of cement containing high alkali metal impurities.
Strengthen the control of construction water quality.
Reduce the contact between the surface of the castable and the air. Surface coatings, coverings, etc. can be used to close the surface pores and minimize the diffusion of CO2 and water vapor into the castable to prevent damage reactions.
Accelerate hardening, dry the green body as soon as possible, promote the development of green strength, and make the damage reaction lose conditions.

After a period of operation, the damage to the original furnace lining has been restored, and the damage to the furnace lining material has not been aggravated. Therefore, when using castables, we should take correct measures in time to make good transformation of the boiler. Rongsheng amorphous refractory castable manufacturer is a powerful manufacturer and seller of refractory materials. To purchase refractory castable products for furnace lining, please contact Rongsheng for free samples and quotations.

Coke Oven Refractory Gunning Material Coating – High Temperature Lining Construction

March 1, 2024 by rsrefractorycastable

Refractory gunning material is an unshaped refractory material used to repair the lining of thermal equipment using spraying construction methods. It is composed of refractory aggregates, binders and admixtures proportioned according to particle gradation, including active coagulants, sintering aids mineralizers, etc.). Generally they are thermosetting or air-setting materials. Gunmetal repair is usually a repair method used when a small part of the interior of the furnace lining is prematurely damaged, but most of it is still relatively complete. It can achieve balanced damage to the furnace lining. Its characteristics are that the construction is simple, the construction period is short, and the construction does not require templates and formwork. It can effectively extend the life of the furnace lining and reduce the consumption of refractory materials.

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Coke Oven Refractory Gunning Material Coating Materials – high temperature resistant adhesive products

The high-temperature resistant adhesive can be used for hot repair of unevenness, erosion, cracks, melting, and falling bricks in the coke oven carbonization chamber and other parts. This product has high refractoriness, high flexural strength, good adhesion, easy hanging and long hanging time. No bubbles or cracks, strong wear resistance, and good construction performance.

Performance Advantages of Coke Oven Refractory Gunning Materials

Good high-temperature performance. When using this product to repair coke ovens, there is no need to cool down, just spray the repair directly and then put it into operation. It greatly shortens the coke oven repair time, reduces production costs, improves work efficiency, and has obvious energy-saving effects.
Under the action of a high temperature of 1000℃, this product has high bonding strength with the silica bricks in the coke oven carbonization chamber. It is also wear-resistant, shock-resistant, peel-resistant, strong and durable.
On-site construction is convenient and not affected by seasonal temperature.
Long service life, its service life is 7-10 times that of similar products currently used in China, and the hanging time is longer.

Coke oven refractory gunning material coating material – high-temperature resistant binder product overcomes the characteristics of large pores, poor wear resistance and short hanging time of similar products on the market. The high-temperature-resistant binder for coke ovens is acidic and should be stirred evenly before use. When repairing the wall of the gunnery furnace, the wall should be cleaned first to make the mud easy to hang. Clean it before spraying. The spraying surface should be flat and smooth and should not be higher than the wall. When the adhesive is relatively viscous, you can add a small amount of water to dilute it before use.

Refractory Spray Paint Lining Construction

Start by welding metal grabber nails or metal mesh to the furnace shell. Load the refractory spray paint that is dry-mixed or semi-dry-mixed with a forced mixer into the spray machine. Use compressed air (wind pressure is 0.10~0.15MPa) to send the mixture to the nozzle. Add an appropriate amount of water or chemical binding agent to mix with the material, and spray it to the sprayed surface. The nozzle outlet should be perpendicular to the sprayed surface, and the distance should be 1 to 1.5m. The spraying of the lining should be carried out continuously, and the thickness of each spraying layer should be less than 200mm. When the lining is too thick, it should be sprayed in layers, but it must be done after the previous layer has sufficient strength. After the lining is sprayed, level the working surface in time and remove the rebound material. The maintenance and baking of refractory spray paint linings are the same as those of refractory castable linings.

What is flame spraying material? Flame gunned material is a shaped refractory material composed of refractory powder, combustion accelerant, and sintering agent.

Compared with other gunning and spraying, flame gunning has strong gunning ability, short time, and fast drying. Gunmetal has the characteristics of high volume density, relatively low porosity, and long service life.

The main raw materials of flame spraying materials are magnesia, magnesia dolomite, and magnesia chromium sand. The sintering agents used are soft clay, bentonite, and silica fume. The combustion accelerant is coke powder, aluminum powder, etc. The flame gunning layer is used as the refractory slag layer, which is to protect the refractory brick layer with lining and hanging slag.

High Temperature Resistant Adhesive Refractory Products — High-Temperature Resistant Adhesive Refractory Products

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Flame spraying materials are mainly used in the slag line and furnace cap of the converter and are also used in steelmaking electric furnaces and ladles. When gunning on the converter, gunning can be carried out when the lining temperature is around 1500°C, and the gunning time is 4-7 minutes. That is to say, spraying can be carried out directly without stopping the furnace.

Gun spraying is carried out using a spray gun, and there are two methods of gunning: horizontal and vertical. When gunning in the converter, gunning can be started after tapping and pouring slag. At first, the spray gun jacket needs to be cooled with water, and then the spray gun can be moved up and down, or it can be rotated and inserted into the furnace. After oxygen supply and spraying, the material is sprayed out from the nozzle of the spray gun.

Because the combustible gas and oxygen mix and burn, the combustion accelerant ignites. The flame-spraying material is melted within a distance of 1.5mm and then sprayed onto the sprayed surface. Then it is sprayed into a gunning layer. After spraying, it can be loaded and used immediately without baking.

Flame spraying materials for converter linings have been developed and used in my country for more than ten years, and the results have been good. However, the use of other furnace linings has not been significantly developed and used. Because the construction of the spray gun is subject to certain restrictions and it is inconvenient to transport it back and forth, it is only used fixedly on some converters. Other furnace lining developments have not yet used this gunning method.

Functional Mechanism and Use of Water Reducing Agent for Unshaped Refractory Materials

November 20, 2023 by rsrefractorycastable

A commonly used additive for unshaped refractory materials is water reducing agent. It can reduce water consumption without affecting the workability of monolithic refractory materials. Or it can increase the workability of unshaped refractory materials without affecting water consumption. Additives that combine the above two properties are called water-reducing agents, also known as dispersants.

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The mechanism of action of water-reducing agent

Change the physical and chemical properties of powder

In the unshaped refractory material industry, solid particles (such as cement, clay, ultrafine powder, etc.) are usually used as dispersants, water is used as the dispersion medium, and additives are treated as solutes. In this system, the particles have a certain surface energy, which has the tendency to absorb electrolytes and surfactants from the solution to reduce the surface energy and cause the system to be in a stable state. It is the powder that selectively and preferentially adsorbs water-reducing agent ions, making it easy for water to disperse on its surface.

Due to this effect, the water-reducing agent is adsorbed on the interface of liquid-gas, liquid-solid, etc. Reduce the interface energy, destroy the agglomeration of particles, and reduce the frictional resistance of relative movement of particles, thereby improving the fluidity of the mud.

Change the electrical properties of the interface

When solid particles are stirred and coagulated with water, they have an attraction due to the opposite charge of the solid particles. Or the angular collision, adsorption and van der Waals force between particles caused by the thermal movement of solid particles in the solution cause a flocculation-like structure, wrapping a large amount of water. After the water-reducing agent is added, the hydrophobic groups of the water-reducing agent are directionally adsorbed on the surface of the particles, and the hydrophilic groups are directed toward the solution to form a monomolecular film or a multimolecular film. The particle-water system is placed in a relatively stable suspended state, the floc structure is dispersed, and free water is released. Because it can release free water in the condensed structure. Therefore, while maintaining the rheology (workability) of the castable, the unit water consumption can be reduced, or the workability can be improved without changing the unit water consumption, making the material easy to construct and shape.

Peptization of colloidal particles

The colloidal particles are transformed from the flocculation state to the sol state, thereby reducing the flow resistance of the mud and improving the fluidity. This can be achieved by adding appropriate electrolytes or water-reducing agents.

Therefore, the water-reducing agent of monolithic refractory materials is either an interface active substance or contains an interface active substance, or a substance that chemically interacts with the surface of the refractory material to change the surface properties. For the former category, the water-reducing agent must have both hydrophobic and hydrophilic groups.

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Classification of water-reducing agents

Depends on the type of binder used. Water-reducing agents can be divided into water-reducing agents for clay bonding, cement bonding water-reducing agents, sol-gel bonding water-reducing agents, ultrafine powder bonding water-reducing agents, and phosphate and silicate bonding water-reducing agents.

Classified by function: ordinary type, retarding type, accelerating type, air-entraining type, etc.

Classified by chemical properties: anionic surfactants, cationic surfactants, nonionic surfactants, polymer surfactants, and inorganic salt surfactants.

Aluminate cement binding water-reducing agent

There are many water-reducing agents used in aluminate cement, but the following five categories are commonly used. Lignins, naphthalene series, water-soluble resins, salts of hydrocarbyl carboxylates and modifications and derivatives, alkanes, aromatic sulfonates, inorganic salts, and polymers.

In aluminate, cement refractory castables, MF, sodium lignin, alkyl sulfonate, etc. are added. It has a good water-reducing effect, but the retardation is heavy and affects the early strength. When tartaric acid, citric acid, and sodium tripolyphosphate are used alone, the water will bleed significantly, which can improve the compactness of the castable, but the water reduction effect is not great. Therefore, for aluminate cement castables, water-reducing agents should be used in combination as much as possible.

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Water-reducing agent for low cement castables

In low-cement refractory castables, the commonly used admixtures are mainly high-efficiency water-reducing admixtures and dispersants. Its varieties include NNO, MF, NF, JN, SM, humic citric acid, tartaric acid and their salts, sodium tripolyphosphate, sodium hexametaphosphate boric acid, etc. The dosage is generally 0.03~1.0%. When selecting admixtures, they should match the ultrafine powder, and at the same time, the source of the material, ease of use, and cost should be considered. Generally speaking, the water-reducing and dispersing effects of organic admixtures are better than those of inorganic admixtures. In addition, kyanite and sillimanite are also added to make the low-cement refractory castable slightly expand at high temperatures.

However, in practice, water-reducing agents are very beneficial in improving the performance of castables. However, you should still pay attention to the following points when using it:

Use standard dosage to avoid material separation and bubbles;
Pay attention to the quality of the water-reducing agent to avoid affecting the performance of the castable;
The post-mixing method should be used during use to improve the use effect and be easily adsorbed by cement;
Stirring time: It is necessary to mix thoroughly and to introduce less air, and the two must be coordinated;
After adding admixtures, the cement dosage and water consumption should be adjusted in time.

What is the Effect of Adding Steel Fiber to Different Castables

November 2, 2021 by rsrefractorycastable

Adding steel fiber to the refractory castable can enhance the toughness of the castable. Moreover, it can enhance the wear degree and mechanical impact of the castable, and more importantly, improve the thermal shock stability of the castable.

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The critical point of adding steel fiber to the castable is at 1350℃. If it exceeds 1350°C, the steel fiber will not play its due role. Like some castables used at positions exceeding 1400°C, there is no need to add steel fiber. No matter how much it is added, it will not have any effect, but it will increase the cost of the castable.

Like cement rotary kiln, white ash rotary kiln, pellet rotary kiln front and rear kiln mouths can use steel fiber-added refractory castables, because the front and rear kiln mouths have many castings, it is impossible to use refractory bricks for masonry, use steel fiber-added refractory pouring The material is not only resistant to tension and compression, but also resistant to fatigue and abrasion.

Not only steel fibers are added to refractory castables, but also appropriate amounts of steel fibers can be added to plastics and ramming materials to improve cracking resistance and peeling resistance. And in the curing process, adding steel fiber can prevent the linear shrinkage of the castable.

However, the amount of steel fiber added should not be too large, which will cause internal changes in the castable. After the castable is sintered at a high temperature, the expansion coefficient will increase and the thermal conductivity will also increase. Especially during construction, excessive addition of steel fiber will cause unnecessary troubles for construction.

There are many kinds of refractory castables with steel fiber, and there are many grades, such as high aluminum and steel fiber, corundum and steel fiber, mullite and steel fiber, and silicon carbide steel fiber. Compound refractory castable. It’s just that different proportions are added under different circumstances.

However, the amount of addition is a technical field, but if the temperature exceeds 1350 ℃, do not add steel fiber, not only does not work. On the contrary, the increase in cost also adds inconvenience to the construction.

Causes of Damage to Blast Furnace Hot Blast stove

October 14, 2021 by rsrefractorycastable

The main reasons for the damage of the hot blast furnace include:

The masonry quality is not ideal, and the construction and acceptance are not carried out according to the masonry specifications;
The quality of the high-strength refractory fire castable in the hot blast pipe and the combustion pipe area is defective, which causes the upper brick to fall off The lining falls off;
The hot blast stove is changed frequently, which causes a certain degree of damage to the brick lining;
The operation of the furnace is not standardized, resulting in low-frequency pulsation of gas combustion, forming gas surge combustion, as the combustion capacity increases
Structural cracks occur when the hot blast stove cools down;
The arch roof combustion temperature exceeds the prescribed standard, and the arch roof fire brick lining is exposed to thermal stress and causes denudation;
The hot blast stove oven does not strictly follow The curve is controlled, and the oven effect is not ideal, which affects the life of the hot blast stove;
The daily operation and maintenance of the hot blast stove is not in place, and effective maintenance and repair measures are not taken for the hot blast stove and local redness;
The hot blast stove The failure of the monitoring devices and interlocking facilities of the company led to errors in post operation;

The quality of the tooling equipment and refractory materials required for the hot blast stove was low in the selection and selection of the hot blast stove, which affected the service life of the hot blast stove.

In order to prevent the corrosion of the furnace shell steel plate, acid-resistant paint is selected to protect the hot blast stove vault steel plate in the design. Among them, it is the key to choose a reasonable acid-resistant coating suitable for the use conditions of the hot blast stove. Monitoring method: In the past, two methods were mainly used to detect the temperature of the vault of the hot blast stove. One is to use platinum rhodium-platinum thermocouple to detect the vault temperature of the hot blast stove, which is a contact temperature measurement method, which has the advantage of high accuracy, but there are several defects:

The reaction speed is slow, mainly because of the poor performance of the protection tube
Inconvenient installation and operation of thermocouples;

(3) Short working life, there is a large amount of CO gas in the vault of hot blast stove, and CO is reducible, and it is very easy to corrode the thermocouple, which increases the maintenance cost in the later period. The other is to use a single-band infrared optical fiber to detect the temperature of the vault of the hot blast stove, which is a non-contact temperature measurement method, that is, the temperature is detected by measuring the infrared radiation emitted by the measured object through a temperature probe.

Features of Lightweight Insulated Castable

June 16, 2021September 19, 2019 by rsrefractorycastable

Lightweight insulation castable is the lower volume density of the castable, the basic volume density of about 1.5. The castable has many pores. Low volume density, small thermal conductivity, good insulation effect and other advantages. It is made of aluminate cement, high aluminum fine material, ceramsite, and additives.

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The lightweight insulation castable good workability, strong adhesion. Strong anti- permeability, no acidizing treatment is needed, which is beneficial to ensure the compactness and fullness of the mortar seam of masonry, and can significantly improve the air tightness, integrity and anti-corrosion ability of the chimney lining.It is an ideal cementing material for lining of high chimney, high temperature flue and air duct.

This series of refractory castables has the following features：

The heat preservation castable volume light, high compressive strength, acid and acid gas corrosion resistance, heat insulation, heat preservation, low water absorption.
It many air holes, low volume density, small thermal conductivity, good insulation effect.
Good workability, strong adhesion, long initial setting time and operation time.
The strength of lightweight insulation castable increases fast, the impermeability is strong, can significantly improve the lining of air tightness, integrity and corrosion resistance.

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The castable is widely used in electric power, petrochemical, metallurgy, kiln and other industries, and can also be used in non-ferrous metallurgy and other industries acid-proof pool and other acid-proof projects.

We are a professional light insulation castable manufacturer, in the production and construction of the professional technical team, rich experience, service in place, welcome to buy the needs of friends, contact us at any time.

Advantages Of Monolithic Refractory

June 16, 2021January 18, 2019 by rsrefractorycastable

Monolithic refractory has many different varieties according to their construction type. These products have their own characteristics and advantages. Generally speaking, The production of monolithic refractory materials is only through the preparation of granules, powder materials and the mixing process of the mixture. Monolithic refractory material has the advantages of simple production process, short production cycle, low heat energy consumption, good integrity in use, strong adaptability and good comprehensive use effect. If you are in need of them, please feel free Contact Us For Free Quote!

Steel Fiber Reinforced Refractory Castable

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What Is Monolithic Refractory

Monolithic refractory is the name normally given to all unshaped refractory products, the word monolithic coming from the word monolith meaning “big stone”. Unshaped refractory materials have different states such as wet, semi-wet, or dry, and can be directly used to construct or repair industrial furnace linings.

Unlike the fired-shaped refractory products, the construction of the lining body with such materials can form a seamless joint inner lining, so it is also called jointless refractory material or monolithic refractory material in Europe and the United States.

Because such materials are formulated and constructed in a similar manner to ordinary building concrete, they are also known as refractory concrete in Eastern Europe and Russia.

Construction of Insulating Castable Refractory Lining

Refractory Lining of the Heating Furnace

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Monolithic Refractory Advantages

The use of monolithic refractory materials is more advantageous than brick masonry in different types of furnaces. Major advantages of monolithic refractory are as follows:

Simple preparation process, short production cycle and high labor productivity

Strong Adaptability. Monolithic refractory can be made into any shape without being restricted by the shape of industrial furnace structure.
Good integrity, good air tightness, large thermal resistance, can reduce heat loss and energy saving in industrial furnaces.

Easy to mechanize construction, save labor and time.

For damaged industrial furnace linings, it is easy to repair with unshaped refractory materials, which can prolong the service life of lining and reduce refractory consumption.

Therefore, many fired refractory products have been gradually replaced by monolithic refractory material, and the proportion of unshaped refractory material used in the metallurgical industry has accounted for 45% – 70% of the total refractory material usage.

So if you are looking for high quality monolithic refractory, there is no doubt that RS will be your best choice! Just Contact Us For Free Quote!