Yearly Archives: 2023

Dec 23, 2023

Are Chrome Corundum Bricks Expensive? How Much Does per Ton Cost?

Chrome corundum brick uses Al2O3 as raw material, adds an appropriate amount of chromium oxide powder and chromium corundum clinker fine powder, and is shaped and fired at high temperatures. The chromium oxide content of sintered chromium corundum bricks is generally lower than that of fused chromium corundum bricks. It can also be prepared by the mud casting method. α-Al2O3 powder and chromium oxide powder are evenly mixed, and a debonding agent and an organic binder are added to form a thick mud. At the same time, part of the chromium corundum clinker is added, and bricks are made into bricks by grouting, and then fired. It can be used as glass kiln lining, brushed glass flow hole cover brick, and used in molten iron pretreatment devices, garbage incinerators, coal water slurry pressurized gasification furnace backing, etc.

Currently, the application of chrome corundum bricks has a wider range of applications. One is chromium corundum brick made of metal chromium slag as the main raw material. This product is widely used in zinc smelting electric furnaces and volatilization kilns. Chromium corundum bricks have good thermal vibration stability and high-temperature creep properties. At the same time, it meets the requirements of the circular economy.

Application and Development of Chrome Corundum Bricks

Based on the good corrosion resistance and thermal shock resistance of chromium corundum bricks. The promotion and application of chromium corundum materials will effectively extend the operating life of pool furnaces and produce long-term economic benefits.

Use chrome corundum bricks to make kiln pool wall tiles

Chrome corundum bricks were used as a replacement for corroded tank wall bricks, including electric bricks, in a cross-fired tank kiln. The tiles came into contact with the glass liquid immediately after installation, but no cracks occurred during the installation process. The kiln was shut down after 3 years of operation. There were only a few large erosions of 50mm at the liquid level. Glass companies that use chrome corundum for tiling have never seen any impact of tinting on the quality of the glass.

Use chrome corundum material to make key parts of the inner layer of the kiln

Refractory bricks based on chromium corundum oxide ceramic bonding have been used in various parts of the inner layer of glass furnaces for many years. The application scope of this refractory material involves the very critical inner parts of glass wool, mineral wool, and soda-lime vessel glass kilns. Such as the corners of the feeding end and the liquid hole as well as the inner layer of the entire kiln. Continuous improvements to this material have resulted in even better performance. RS refractory material manufacturers can produce various types of chromium corundum products with chromium oxide content from 10% to 70%. To extend the life of the pool furnace, research chromium corundum materials with corrosion resistance comparable to isostatically pressed products, and reduce costs.

Years of practical application of chromium corundum refractory materials have shown that its strong corrosion resistance and erosion characteristics fully meet the design requirements. In soda-lime glass furnaces, they protect key furnace parts very well and also enable the corrosion-resistant fiberglass furnace to have a furnace life of 4-5 years.

Chrome corundum bricks for garbage incinerators

Waste incinerator is a common thermal equipment in municipal waste treatment. According to different incineration methods, it can be divided into intermittent incinerators, grate incinerators, CAO incineration systems, fluidized bed incinerators, rotary kiln incinerators, etc. Among refractory materials for incinerators, refractory materials containing chromium oxide have good corrosion resistance. When the temperature is greater than 1250°C, chrome corundum bricks can be used as the lining of the incinerator.

The Al2O3 content in chromium corundum bricks used in garbage melting incinerators is 83.5%, and the Cr2O3 content is 9.3%. The bulk density is 3.09g/cm3, and the normal temperature compressive strength is 91.8MPa.

Abroad, the aggregate particle size of chrome corundum bricks used in garbage melting furnaces is less than 2.5mm, mainly corundum, and the dosage accounts for 20% to 30%. Chromium oxide is only 2%, while the chromium oxide content in fine powder is relatively high, around 5%. From the composition difference between aggregate and fine powder, it can be confirmed that the brick is sintered at medium temperature and the binder is phosphate.

Regarding chrome corundum bricks, Rongsheng Refractory Materials, as a professional refractory brick manufacturer, has complete quality testing standards and monitoring systems. Rongsheng adopts the double-three inspection method, strict self-inspection, random inspection, and re-inspection procedures. Ensure that each batch of refractory materials can meet the user’s standards so that customers can buy with confidence and use them with confidence.

Are chrome corundum bricks expensive? How much does a ton cost?

Chrome corundum brick is a special product with chromium added to the corundum brick. It has good wear resistance, corrosion resistance, high-temperature resistance, impact resistance, and other properties. Prices vary based on market demand and differences in chromium content. Generally, the price of chromium corundum bricks with a chromium content of 5% to 10% is about 13,000 yuan/ton, while the price of chromium corundum bricks with a chromium content of 30% to 50% is more than 20,000 yuan/ton. The price of chrome corundum bricks is closely related to market demand. When market demand is high, prices will rise accordingly; when market demand is low, prices will fall. In addition, the difference in content is also a key factor affecting the price of chromium corundum bricks. The higher the chromium content, the higher the price.

In actual production, the price of chrome corundum bricks is also affected by other factors, such as production costs, production processes, sales channels, etc. The rising production costs, including raw material procurement costs, production equipment costs, labor costs, etc., also directly affect the price of chrome corundum bricks. In addition, the production process of chrome corundum bricks will also affect its price. High-end production technology will make the price of chrome corundum bricks higher. At the same time, different sales channels will also lead to differences in the price of chrome corundum bricks. The price purchased directly from the manufacturer may be lower than the price purchased from agents or dealers. Based on the above factors, the price of chrome corundum bricks is not only related to chromium content but also related to market demand, production cost, production technology, and sales channels. The prices of chrome corundum bricks of different specifications and quality will be different. If you need to purchase chrome corundum bricks, it is recommended to choose a reliable brand and channel for purchase after making multiple comparisons.

Nov 27, 2023

How to Use Ceramic Roller Properly?

Since ceramic rollers operate under high temperatures and loads for a long time, various problems are prone to occur during the production process. Such as the middle break, the replacement roller burst, the roller head cracks, bending in the kiln, etc. Most of these problems are caused by the service life of the rollers, and some are caused by the quality of the product itself or improper operation. So, do you know what problems will occur when using ceramic rollers? What is the correct way to use ceramic rollers? Industrial ceramics factories will provide reference answers.

What are the Common Problems with Ceramic Rollers?

Common problems in the use of ceramic rollers are mostly caused by defects in the rollers.

1 middle break

The roller is broken horizontally, with neat fractures and loose cross-section, also called horizontal breaking. The main reasons for the breakage of the roller rod are as follows.

(1) The kiln firing temperature is too high. For example, the operating temperature of medium-temperature rollers is within 1000°C, the operating temperature of medium-high-temperature rollers is within 1200°C, and the operating temperature of high-temperature rollers is within 1250°C. If this extreme temperature is reached or exceeded, the phenomenon of roller breakage will increase significantly.

(2) The influence of roller load, span, and speed. When producing ceramic tiles or other products with larger specifications, the heavier the weight of the product, the larger the width of the kiln (more than 2.7m), and the larger the span of the rollers. The faster the roller rotates, the greater the chance of roller interruption.

(3) Improper selection of rollers. When producing ceramic tile products with specifications above 600mm×600mm, it is best to use a Φ50mm roller. To produce products of 800mm×800mm and above, it is best to use rollers with Φ60mm or Φ65mm specifications. The production of daily-use porcelain or other rare earth raw materials that are loaded and unloaded in the form of saggers or backing plates requires the high strength of the roller, so ultra-high temperature rollers should be selected.

(4) The roller rod is severely corroded. Since the roller rod has been running in the kiln for a long time and is affected by the kiln pressure, kiln atmosphere, and fuel-corrosive gas, the roller rod has a certain service life. Generally, the strength of the roller will gradually decrease after being used for more than two months, and interruptions may occur under load. The main manifestations of this type of broken rod are neat fracture, loose cross-section, and color on the surface of the cross-section.

(5) The roller itself is not strong enough. If the new rod penetrates into the high-temperature area of the kiln and naturally breaks after a few days of operation, it is a quality problem with the product itself. This type of broken rod has neat fractures and loose cross-sections, but the surface of the cross-section is colorless.

2 The roller exploded when replacing it.

The main symptoms of explosion when changing the rod are crack lines along the length of the roller rod and two or more fractures. Or it may be broken, with uneven fractures and smooth cross-sections. The main reasons for the explosion are as follows.

(1) The rod replacement temperature is too high. The temperature for normal roller replacement is best controlled at 800~850℃ and should not be too high. At the same time, as the diameter and length of the roller rod increase, the surface area of the roller rod increases, and the thermal stability of the roller rod gradually becomes worse. During the process of changing from high temperature to normal temperature, the temperature inside and outside the roller rod is inconsistent, resulting in an explosion.

(2) Improper rod replacement operation. When pulling the rod, the red high-temperature part of the roller comes into contact with a good conductor of heat such as iron. During the cooling process, the contact point of the roller shrinks sharply, causing it to explode. If there are water stains on the ground where the roller is placed or if the roller is forced to cool with wind, it will also cause the roller to burst.

(3) The protective coating is not dry yet. The coated roller contains more crystal water and adsorbed water. The roller must be placed beside the kiln to fully dry before use. Otherwise, when entering the high-temperature area, the roller rod will burst due to the rapid evaporation of water.

(4) The roller rod is severely corroded. The rollers were corroded by corrosive gases in the kiln, causing obvious structural variations in the cross-section of the rollers (comparison of old and new rollers), or delamination in the cross-sections of the rollers. It is easy to burst, linearly crack, or break into several sections during the cooling process. The color of the surface of the eroded roller changes significantly.

(5) The adhesion of blank or glaze droplets on the surface of the roller rod is too serious so that the pores on the surface of the roller rod are blocked, the porosity changes and the inner and outer shrinkage is inconsistent during the cooling process, leading to an explosion. The roller bar after sticking the rake is shown in Figure 3.

(6) Due to the poor thermal stability of the roller itself, the roller is prone to bursting when it is inserted into the high-temperature section of the kiln after preheating in the low-temperature section. The fracture of this type of broken rod is uneven, smooth, and colorless. See Figure 4.

3 The roller rod is broken and broken.

The main causes of roller cracks and broken ends are:

(1) The outer diameter of the roller rod does not match the inner diameter of the kiln transmission sleeve. The sleeve itself has tolerances, and the tolerance of a normal sleeve is 0~0.2mm. In actual production, there are problems such as the inner diameter of some sleeves being too small, so that the inserted roller rod is too tight and a broken head occurs.

(2) The kiln transmission sleeve is deformed due to inconsistent operation after the roller is inserted. Twist the roller rod and break the end. Deformation of the kiln wall or displacement of the kiln hole bricks can also lead to roller breakage.

(3) Excessive force when inserting the roller into the sleeve can easily cause the roller to crack.

(4) The roller itself has dark cracks. After being inserted into the kiln, cracks will appear under high-temperature conditions, and breakage will gradually occur after the sleeve is inserted. The split head stick is shown in Figure 5.

4 Bending deformation

There is a certain correlation between the bending deformation of the roller and the interruption of the roller. The main reasons for the bending deformation are:

(1) Because the current firing cycle of ceramic products is relatively certain. When the firing cycle is constant, the longer the kiln, the wider the internal width, the faster the roller rotation speed, the higher the firing temperature, and the easier it is for the roller rod to undergo high-temperature bending deformation.

(2) Due to the influence of the quenching air curtain in the quenching zone of the kiln, the bricks need to be cooled from the highest temperature to 600-700°C in a short period of time. The temperature difference between the upper and lower rollers in this area is quite large, and the rollers are prone to bending.

(3) It is worth noting that if individual rollers of different batches of products are bent and deformed under basically the same conditions of use, it should be caused by quality problems of the roller itself.

How to use ceramic rollers reasonably?

1. The inner cavities at both ends of the newly purchased ceramic roller should be filled with 100mm long ceramic loose cotton and a mark should be made on one end of the roller. Use it once in the kiln and mark it once to determine the length of use.
2. The surface should be coated with a protective coating before entering the kiln. The sizing length is generally 100mm longer than the effective width in the kiln, and the thickness is between 0.8 and 1.2mm. Sizing can be done in two steps, and the surface must be cleaned before sizing.
3. Ceramic rollers should be preheated and dried for 24 hours before being loaded into the kiln.
4. After applying the base paint, the dirty roller should be replaced in time. Generally, it is better to cool down to 800℃ and replace them centrally.
5. Whether loading or unloading the kiln, it must be as fast as possible. The extracted ceramic roller must adopt the correct cooling method to prevent “wind shock” caused by local rapid cooling.
6. The extracted product must be cooled using the correct method. Do not place it directly on the ground. Generally, a mechanical rotating stand and a cold roller are used. After exploration, the vertical suspension cooling method saves people and effort, and the effect is good.
7. After the replaced dirty ceramic roller is polished, its straightness, diameter, etc. must be carefully checked for reuse.
8. Choose a reasonable blank formula and brick primer. The surface coating liquid can reduce the chemical corrosion of the body and reduce the occurrence of roller breakage accidents.

To purchase high-quality ceramic rollers, please choose a strong ceramic product manufacturer.

Nov 2, 2023

Slag-Resistant and Corrosion-Resistant High-Alumina Special-Shaped Refractory Bricks

High-alumina special-shaped refractory bricks that are resistant to slag and corrosion. The slag resistance of high-alumina special-shaped bricks increases with the increase of Al2O3 content. Reducing the impurity content is beneficial to improving corrosion resistance. The difference between high alumina refractory bricks and clay bricks is that high alumina refractory bricks have good performance. Therefore, high alumina bricks have a longer service life than clay bricks.

Slag-Resistant and Corrosion-Resistant High-Alumina Special-Shaped Refractory Bricks

Classified from the appearance, high alumina refractory bricks are mainly divided into standard bricks, ordinary bricks, wedge-shaped bricks, special-shaped and special-shaped bricks. Depending on the part used, we will choose different shapes. Sometimes if the location of the kiln is special, we can also customize special-shaped high-alumina bricks for use.

High alumina runner brick is a kind of special-shaped high alumina refractory brick. It is a hollow refractory brick built in the groove of the bottom plate for ingots and connected with the steel bricks and the steel ingot mold. It is commonly known as the soup road brick. Steel Runner Bricks has various specifications of rectangular hollow high alumina bricks. In order to reduce the resistance during the flow of molten steel and prevent steel leakage, the inner hole of the flowing steel brick is required to be smooth, the shape is regular, and the joints are tight. Steel runner bricks are widely used in flat steel castings of various steel types (including stainless steel and various alloy steels). High alumina runner brick products have high refractoriness, good cracking resistance, and strong corrosion resistance. The appearance is regular, the channel is smooth, the size is accurate, and the variety is complete. Produces ladle lining bricks, curved lining bricks, fired and unfired plug bricks, sprue bricks, seat bricks, and sleeve bricks for cast steel in ladles. High-quality raw materials and unique technology enable the product to have good high-temperature physical and chemical properties, and resistance to erosion, deformation, and shedding.

Steel runner bricks are used for slab steel pouring of various alloy structural steels (including stainless steel and various carbon steels). The product has high fire resistance, strong chipping resistance, and strong adhesion resistance. The appearance is neat, the channels are smooth, the specifications are precise, and the quality is high. Clay bricks for ingot casting refer to the clay bricks commonly used in the process of introducing molten steel into the ingot mold from Shenggang. Including ladle lining bricks and steel casting bricks. Among them are sleeve bricks, plug head bricks, water position bricks, seat bricks, molded pipe bricks, central cast pipe bricks, central bricks, steel runner bricks, flow steel tail bricks, and steel ingot mold bottom bricks.

Steel runner bricks are usually rectangular hollow clay bricks with various specifications. In order to reduce the friction resistance during the flow process of liquid steel and prevent steel leakage, it is required that the inner hole of the steel runner brick is smooth, the appearance is neat, and the joints are tight. Steel runner bricks are the application of hollow corundum bricks and related refractory bricks that are connected to the steel runner bricks and steel ingot molds in the trench of the ingot casting plate, also known as soup road bricks. Steel runner bricks are usually rectangular hollow clay bricks with various specifications and models. In order to reduce the friction resistance during the flow process of liquid steel and prevent steel leakage, it is required that the inner hole of the steel runner brick is smooth, the appearance is neat, and the joints are tight.

Special high alumina brick

Special high alumina brick is a new type of chemically bonded high alumina refractory brick. It overcomes the weaknesses of high alumina refractory bricks such as poor thermal shock performance and low normal temperature compressive strength. It has the advantages of chemical corrosion resistance and high strength of phosphate refractory bricks. Moreover, it is easy to hang the kiln skin and is a new type of refractory brick for firing zones. The refractory mud used in high alumina bricks and the preparation method are basically the same as those of clay bricks. High-strength refractory mud can also be used.

High alumina refractory bricks are generally used in steel, steelmaking, hot blast furnaces, electric furnace tops, blast furnaces, reverberatory furnaces, rotary kiln linings, and other industrial kilns in China. The main components are high-alumina bauxite and sillimanite minerals (including kyanite, red base stone, sillimanite, etc.). Artificial synthetic materials, such as industrial alumina, synthetic mullite, fused corundum, etc.

High alumina bricks have the characteristics of good service quality, high refractoriness, and long service life. They are the primary refractory brick products used in industrial kilns. Generally, business units cannot correctly distinguish the quality and grade of high alumina refractory bricks when purchasing high alumina bricks. It is easy to buy low-grade high-alumina brick products at high prices. The service life of the kiln is reduced, so that smooth production cannot be guaranteed during use. Therefore, RS refractory material manufacturers remind companies to distinguish between high-quality high-alumina bricks and low-grade high-alumina bricks when purchasing high-alumina refractory bricks. It can be identified from the following aspects. Color: When purchasing high alumina bricks, you must first look at the color. Excellent high-alumina bricks have a smooth surface, yellowish-white color, flat sides, no broken corners, and no cracks.

High-quality refractory bricks, high-alumina bricks, high-quality raw materials, and unique processing techniques make the products have excellent high-temperature physical and chemical properties. It is corrosion-resistant, non-deformable, and not easy to fall off from the kiln lining.

How to Choose a High Alumina Brick Company?

The golden rule for choosing high-quality high-alumina special-shaped bricks.

1. Choose a high-alumina brick company with a large scale.
2. Choose a high-alumina brick company with good technology.
3. Choose a manufacturer of special-shaped bricks with high cost-effectiveness.

RS Refractory Material Manufacturer is a powerful refractory brick manufacturer. Our shaped refractory brick products have an annual output of 6W tons. Refractory products have been sold to more than 100 countries around the world. For example, South Africa, Chile, Egypt, Colombia, Uzbekistan, Italy, Indonesia, Ukraine, Hungary, Spain, Kenya, Syria, Zambia, Oman, Venezuela, India, Peru, the United States, Ethiopia, etc. Moreover, our professional technical team will provide you with customized refractory lining material solutions based on the actual working conditions of your high-temperature industrial furnace. Our comprehensive high-temperature industrial furnace lining refractory material services will provide you with a complete service system to ensure the efficient and long-life operation of Ningde high-temperature industrial furnaces.

Oct 12, 2023

Affordable Refractory Plastic Furnace Linings from the Manufacturer

Refractory plastic is a plastic refractory material made by mixing mainly refractory aggregates and powders, adding appropriate binding clay, binders, and admixtures. RS Refractory Materials Manufacturer can provide cost-effective refractory plastic furnace linings. According to the performance requirements of refractory plastic furnace linings, its varieties include clay, high alumina, silicon, magnesia, magnesium chromium, and silicon carbide. The most widely used refractory plastics in soaking furnaces are clay and high alumina.

Application of Refractory Plastics in Soaking Furnaces

In the early stage of the application of refractory plastics in soaking furnaces, the furnace lining is damaged due to the breakage of the anchor bricks, and the service life is generally 12 to 15 months. Later, the shape and arrangement spacing of the anchor bricks were changed, which greatly improved the service life of the refractory plastic furnace lining. Generally, it is three times or more than the service life of the refractory brick lining. That is about five years.

China has repeatedly tried refractory plastic on the furnace walls and lids of large soaking furnaces, and its service life is basically the same as that of refractory brick furnace linings. On the walls of soaking furnaces in special steel plants, refractory plastic ramming furnace linings are often used. The service life is generally 4 years, and some are still in use.

The performance of refractory plastics used in soaking furnaces. These materials are also used on the furnace ends and tops of heating furnaces with good results. It should be pointed out that in Japan, it is common to use refractory plastics to build furnaces in soaking furnaces. In the early 1960s, Japan introduced this technology from the United States and developed rapidly from trial to trial production of new products. By the late 1960s, more than 95% of soaking furnace covers were lined with refractory plastic, and their service life was generally 2.0 to 2.5 years. Refractory plastics are also commonly used on furnace walls, with a service life of 3 to 1 year. After several minor repairs, its lifespan can reach more than 5 years. In the 1970s, the application of refractory plastics in soaking furnaces reached a finalized design and was directly supplied by manufacturers according to brand requirements.

The Service Life of the Refractory Plastic Lining of the Soaking Furnace

The service life of the refractory plastic lining of the soaking furnace is closely related to the structure type of the furnace body. That is, the quality of the anchoring and hanging system directly affects the use effect of the furnace lining.

Anchor bricks and hanging bricks are movablely connected to the furnace shell or steel structure, and their main bodies are embedded in the refractory and plastic furnace lining, forming a unified whole. It can resist the inclination of the furnace wall, structural peeling, and abrasion damage caused by temperature and mechanical collision, thereby extending the service life of the furnace lining.

Anchor bricks and hanging bricks are generally made of high-aluminum materials with an Al2O3 content equal to or greater than 60%. The volume density is about 2.34 g/cm3, the compressive strength is greater than 400 kg/cm3, and the linear expansion after reheating at 1500°C is about 0.05%. Its cross-sectional size is 100×120 (or 180) mm. The length should be greater than the thickness of the furnace lining and the metal parts should be kept away from high-temperature areas or exposed to the air as much as possible to increase the life of the bricks and facilitate disassembly and repair.

The spacing of furnace wall anchor bricks is generally 400×400 mm or 500×500 mm. If the furnace wall is high, supports can be installed appropriately to enhance stability. Supports are divided into two types: metal and non-metal. When installed, it must be fixed and kept away from the working layer of the furnace wall. The anchor bricks for the furnace wall around the burner are best arranged in a plum blossom shape, and metal anchors can be added if necessary.

The spacing of furnace roof hanging bricks is generally equivalent to the thickness of the furnace roof lining, and the common size is 300×300 mm. The hanging bricks are hung on metal tie beams using metal parts and are firmly fixed with wooden deeds during construction. A gap of 5 mm should be left between the bottom of the hanging bricks and the formwork so that the hanging bricks can be stressed evenly after the formwork is removed and to prevent damage to the furnace lining.

Configuration of Refractory Plastic Lining of Soaking Furnace

The spacing of hanging bricks on the flat roof of the furnace cover is 300×300 mm, and the spacing on the sloped roof part is smaller. It is made of refractory plastic with an Al2O3 content of 45% and a thickness of 230 mm. A 50 mm thick lightweight refractory castable is poured on the upper surface as a heat insulation layer. The furnace mouth is built with high-aluminum bricks with an Al2O3 content of 60%, or it can be made of refractory plastic of the same material. The spacing of the furnace wall anchor bricks is 400×450 mm, the total thickness of the side walls is 645 mm, of which the insulation board is 65 mm, and the partition wall thickness is 456 mm. The bottom of the furnace wall is made of refractory plastic with an Al2O3 content of 80% to resist erosion by slag. The remaining parts are made of clay refractory plastic with an Al2O3 content of 45%. The working layer of the furnace bottom is made of clay bricks, and the insulation layer is made of lightweight clay bricks, diatomaceous earth bricks, and asbestos boards, with a total thickness of 380 mm.

Construction Quality of Refractory Plastics

The construction quality of refractory plastics has a direct impact on the service life of the furnace lining, and it must be operated in strict accordance with technical regulations. Before construction, various refractory materials, machinery, and tools should be prepared to ensure normal construction. The pounding of refractory plastics should be carried out continuously. If there is a temporary interruption, cover it tightly with plastic sheeting to prevent moisture from evaporating. The ramming direction should be parallel to the hot surface of the furnace lining construction body, that is, the furnace wall should be rammed vertically and the furnace top should be rammed horizontally. The walking speed of the hammer head should ensure that the ramming surfaces can overlap each other by about 1/2, and the hammering should be repeated 3 to 5 times. The refractory plastic construction layers must be fully integrated and uniform in texture, with no gaps or leaks allowed.

The refractory plastic can be rammed into a place where the anchor bricks will be placed. First, use a wooden or metal mold similar in shape to the anchor bricks to drive it into the plastic lining, then take out the mold and insert the anchor bricks. Then continue to pound the refractory plastic to tightly bond it with the anchor bricks. Otherwise, the anchor bricks will not be able to perform the anchoring function and may cause smoke and fire easily.

A non-penetrating expansion joint should be left at the corner of the furnace wall with a width of 10 to 20 mm. Use wooden boards or plastic corrugated boards as caulking materials to burn them in the oven.

After the entire furnace lining is pounded, it needs to be naturally cured for 24 hours before the formwork is removed and the working surface is renovated. Ventilation holes are drilled with a diameter of 6 to 8 mm, a spacing of 100 to 200 mm, and a depth of 2/3 of the thickness of the construction body. Briefly avoid the anchors and use a cutter to cut expansion joints. The width of the joint is 5 mm and the depth is 40 to 60 mm. The distance depends on the performance of the furnace material, generally 2 to 4 meters. It should be pointed out that it is also feasible to directly use plywood or plastic corrugated boards as expansion joints during construction.

After the construction is completed, the site is cleaned and the oven is carried out within a week. The figure below shows the oven curve of the soaking furnace (220 hours in total). Before 700℃, insert a temporary gas pipe through the slag hole at the bottom of the furnace for baking. There should be a gap in the furnace cover and the flue gate should be closed. After reaching 700°C, close the furnace cover, slightly open the flue gate, ignite the working burner and continue drying until the operating temperature is reached before installing steel for production.

Large-scale refractory plastic prefabricated blocks are generally hoisted mechanically, while small ones are assembled manually. The spacing between anchor bricks is basically the same as mentioned above. When the first layer of anchor bricks is laid, all or at least less than the anchor bricks should be refractory and plastic pounded on site to make the furnace wall form a whole. After the construction of this layer is completed and leveled, hoisting of prefabricated blocks will continue.

RS Refractory Plastic Factory

Using refractory plastic prefabricated blocks to make the furnace wall of the soaking furnace have a service life basically the same as that of the plastic furnace wall that is pounded on site. The speed of furnace construction is increased and the unit price of the project is reduced. Rongsheng refractory material manufacturer can provide high-quality refractory plastics for high-temperature industrial furnaces such as soaking furnaces. Equipped with PA80 glue. RS manufacturer’s refractory plastics can be customized according to the working conditions of high-temperature industrial furnaces. For example, wear-resistant refractory plastics, high-aluminum and high-strength corundum refractory plastics, micro-expansion refractory plastics, and silicon carbide refractory plastics.

Sep 18, 2023

Repair of Refractory Materials in Heating Furnace Lining

Lining repair is a common item in heating furnace maintenance work. There are two main methods of repairing linings. One is to use the same refractory castable as the original lining for repair, and the other is to paste a certain thickness of refractory fiber felt. The construction method and quality requirements for repairing the lining with refractory concrete are the same as those for the new furnace lining. In addition, pretreatment of the repair surface needs to be done.

Construction Method of Repairing Lining with Refractory Castable

Commonly used for repairs of lightweight refractory castable linings. Before construction, materials must be prepared, a detailed understanding of the construction site, and construction tools must be cleaned. The specific pre-construction preparations are as follows.

• (1) Before construction, the repair scope should be reasonably determined based on the damage to the lining. Remove the failed furnace lining within the repair range to meet the pretreatment requirements for repair construction.
• (2) Containers and tools used for lining construction should be cleaned. Prevent lime, other cement, clay, and other impurities from mixing into the aggregate.
• (3) Ceramsite should be soaked for at least 12 hours before use, and excess moisture should be eliminated during use.
• (4) The parts of various pipe racks, casings, and other metal components (except insulation nails) buried in the lining should be coated with 0.5~1.0mm thick asphalt.
• (5) The construction site should be maintained between 10 and 25°C, and cooling or warming measures should be taken accordingly in summer or winter. After the curing is completed but not in the oven, the temperature should be kept above 5°C to prevent freezing damage to the lining.

The construction method of repairing the lining with refractory concrete can be carried out in the following three methods depending on the materials used.

1. Smearing method

During construction, the steel wire mesh must be filled with castable. There must be no holes and the concrete must be dense. When applying, spread the concrete and smooth it with a wooden trowel until the surface is rough. To prevent cracks, the castable surface cannot be calendered. This method is suitable for small-area lining repairs.

2. Spray coating method

The semi-dry method should be used for spraying, that is, the refractory material should be properly moistened with water and stirred evenly before adding it to the sprayer. When spraying, the material and water should be sprayed evenly and continuously, and there should be no dry material or flow on the spray surface. The nozzle should continuously move in a spiral manner to distribute coarse and fine particles evenly. Spraying should be carried out in sections and continuously, reaching the thickness at one time to avoid delamination. If the thickness cannot be reached at one time, layered spraying can be used, but the second layer must be sprayed before the initial setting of the previous layer of spray paint. When construction must be interrupted, diagonal stubble should be left at the joints. When construction continues, the joints must be cleaned and moistened with water. During spraying construction, the thickness of the spray coating should be checked at any time. The excessively thick parts should be shaved off, and the surface of the spray coating should not be smoothed. When spraying, a wooden box should be used to leave a test block at the spraying location to check its strength and bulk density. After construction, tap gently with a small hammer to check the density of the sprayed layer. If any holes or interlayers are found, they should be dug and repaired in time. This method is suitable for repairing or constructing new furnace linings in large areas with thick linings (greater than 50mm).

3. Mold pouring

The pouring and loading of the mold into the formwork should be done in layers, and the thickness of each layer should be 150~200mm. In order to prevent the delamination of light aggregate and cement during tamping, which increases the bulk density and affects the thermal conductivity, mechanical tamping should not be used. Manually tamped concrete must be dense and free of honeycombs and voids. When tamping, first tamp around the anchor pin, and then tamp it again with half a hammer, without over-tamping or missing tamping.

Pouring of refractory concrete is best done continuously. When construction must be interrupted, the joints should be “roughed” and covered tightly with plastic film. After 12 hours, pouring can be continued.

When pouring refractory concrete on top of the insulation block, prevent the upper insulation block from absorbing water. The best way is to paint a layer of asphalt on the insulation block, or you can lay a layer of plastic film. If plastic film is spread on a vertical surface, it should be fixed to prevent it from slipping. This method is also suitable for the repair of large-area, large-thickness vertical linings and the lining construction of new furnaces.

Refractory fiber paste repair method

The use of refractory fiber paste to repair the lining is a new method developed in recent years. It has the advantages of simple construction, no need for maintenance, and short oven and maintenance cycles.

When overhauling the lightweight heat-resistant concrete lining of the heating furnace, it was found that the surface of some linings was generally delaminated, powdered and peeled off, that is, the surface layer of the concrete lining lost its strength. The reason for this phenomenon may be the corrosion of the gas medium in the furnace. If you still use raw materials to repair it at this time, you will definitely make the same mistake again. The use of pasted refractory fiber felt is an effective method.

Scrape off the powdery layer on the original lining surface and roughly level it. Large cracks and peeling areas are hand-painted with raw materials, and then a layer of refractory fiber felt is pasted. The thickness of the paste should be determined through calculation, but it should not affect the heating of the furnace tube surface. This composite structure of ceramic fiber felt is vertically attached. The vertical ceramic fiber felt is cut by machine according to the required thickness and tied into bundles.

Before pasting, clean the flattened lining to remove any floating material. When pasting, start from the root of the wall and paste it from bottom to top. Use a paint brush to spread the adhesive on the furnace wall and the ceramic fiber bundle strips respectively, and apply it fully. Then attach the ceramic fiber bundle strips and compact them with your hands. If there is water on the furnace wall or top, the ceramic fibers will not be able to stick to it.

The adhesive should have properties such as high-temperature resistance, strong adhesion, lightweight, and the ability to cure at room temperature. Currently, commonly used adhesive types include:

• (1) Water glass: pulp waste liquid = 1:1 plus 10% clay clinker powder and a small amount of clay powder.
• (2) Aluminum silicate adhesive.
• (3) Methylcellulose.
• (4) Aluminum phosphate adhesive, phosphoric acid: aluminum hydroxide = 8:1.

For example, adding masonry powder to the adhesive to make it into a paste, and adding some MgO can make it stronger at room temperature.

Rongsheng refractory material manufacturers can provide customers with comprehensive refractory material services. Extend the service life of refractory lining materials in high-temperature industrial kilns and reduce the number of furnace shutdowns and repairs. Design and construction of refractory solutions for insulation layers, and turnkey projects of refractory lining materials for high-temperature industrial furnaces. If you are in need of purchasing heating furnace lining refractory materials, refractory brick linings, or unshaped refractory linings, please contact us. Get free quotes and samples.

Sep 18, 2023

RS Monolithic Refractories for Delivery