Introduction to the Ingredients of Acid-Resistant and Refractory Coating Materials
Acid-resistant and refractory coating materials are prepared from acidic or semi-acidic refractory powder (less than 0.088 mm), binders, and coating additives. Acidic and semi-acidic materials that can be used include pyrophyllite, silica, cast stone, andesite, burnt gemstone, etc. Their acid resistance is 92% to 96% for pyrophyllite, more than 97% for silica, 98% for cast stone, more than 94% for andesite, and 92% to 97% for charred gemstone. In addition, in order to prevent cracking during the drying of the coating after construction, heat-resistant glass short fibers or aluminum silicate refractory short fibers (3 to 7 mm) can also be added.
Binder for Acid-Resistant and Refractory Coatings
The binding agents of acid-resistant and refractory coatings include water glass, silica sol, acidic aluminum phosphate (aluminum dihydrogen phosphate), etc. Rongsheng Refractory Material Manufacturers can use high modulus water glass (modulus not less than 3) when using water glass as a binder, and can introduce organic resin to improve its bonding strength and crack resistance. The organic resin is preferably water-soluble or water-based latex resin. Optional organic resins include water-soluble sodium methyl siliconate, polyvinyl acetate emulsion, polyacrylate emulsion, water-based urea resin, etc. When using silica sol as a binding agent, a silica sol with a Si02 content of 30% to 45% should be used. A silane coupling agent or organic resin emulsion can be added when used. When acidic aluminum phosphate is used as a binding agent, it needs to be baked at high temperature to solidify. During the heating process, condensed phosphate is formed to form a film. A curing agent can also be added to solidify it into a film. The curing agents that can be used include metal oxides, hydroxides, borates, silicon cyanide, etc.
Uses of Acid-Resistant and Refractory Coatings
Acid-resistant and fire-resistant coatings are mainly used for smoke windows and flues where acidic gas media passes. and surface coatings for certain linings of reactors with acidic media.
Rongsheng Acid Resistance Castable for Sale
Special Performance Refractory Castable – Acid-Resistant Refractory Castable
Special performance refractory castables mainly include wear-resistant, acid-resistant, alkali-resistant, and high thermal conductivity castables. This type of castable is used in special kilns or locations, so it has special performance requirements.
Acid-resistant refractory castables are formulated with a water glass or cement as a binding agent and siliceous and aluminum silicate materials. Its characteristic is that it still has good performance under the action of medium and low temperatures and acid media. This type of refractory castable is used in blast furnace hot blast furnace dome protective layer, steel chimney lining and other equipment, and achieves good results.
The acid resistance of acid-resistant castables is affected by both physical and chemical factors. When the concentration of the acid solution is small, it will penetrate along the fine cracks of the product. The connection between aggregate and powder is destroyed and the strength is reduced. On the contrary, the acid solution has high viscosity and is difficult to penetrate, and at the same time, the chemical effect is strengthened. That is, the concentrated acid solution has an acidifying effect on the unreacted water glass and precipitates silicate gel to promote the strength growth of the castable.
At present, there is no standard to follow for the acid resistance of unshaped refractory materials. Under normal circumstances, according to the technical requirements of the project, the experimental plan is designed and the acid resistance test is carried out. Rongsheng refractory material manufacturers can customize refractory lining solutions according to the actual working conditions of the kiln lining. Contact us for free details.
The gas penetrates into the refractory bricks from the furnace space, accompanied by a series of physical and chemical processes. This depends on the gas composition, refractory brick composition and temperature. As refractory materials interact with gases, most will lose mechanical strength, thermal shock resistance, and in some cases even refractory resistance.
Chemical Reactions between Refractory Materials and Various Gases
(1) Interaction with water vapor and CO2
Calcium-containing refractory bricks are destroyed due to hydration of water vapor at normal temperatures. The hydration of CuO and MgO increases the volume almost 2 times, causing the bricks to spread out. Hydration products are decomposed at approximately 800°C. It can be seen that hydration will not occur above this temperature. Materials based on alkaline earth metal aluminates, gallates and indiums that improve the stability against water vapor and CO2. In the formula of MO-R2O3, M—Ca, Sr, Ba; R—Al, Ga, In.
(2) Interaction with alkali vapor
Alkali (K2O, Na2O) vapor combines with mullite and metakaolinite to form nepheline K2O·A12O3·2SiO2 and nepheline Na2O·Al2O3·2SiO2. As the reaction proceeds, the volume increases and some parts of the brick simultaneously peel off. The stability of refractory materials against alkali vapor increases in the following order: clay bricks (Al2O3 42%), high alumina bricks (mullite, Al2O3 70%), clay-bonded silicon carbide bricks, corundum bricks, self-bonded silicon carbide bricks, Nitride bonded silicon carbide bricks. According to the relationship between aluminum silicate refractory materials, lithium alkali corrodes the most, followed by sodium, and potassium less. This is related to the lowest melting temperature of lithium alkali and is consistent with the decreasing sequence of K2>Na>Li atomic radius.
(3) Interact with chlorine gas
Chlorine reacts with many refractory oxides to produce fusible or volatile compounds, and its vaporization causes the strength of refractory bricks to decrease. Chlorine destroys refractory materials similar to hydrogen. Perclase refractory materials are the least stable to chlorine (MgCl2 melts and volatilizes at 712°C), while high alumina bricks and corundum bricks are the most stable. It was found that at 950°C, in contact with chlorine for 72 hours, the strength of magnesite bricks and chromium magnesia bricks was reduced by 100%, clay bricks by 24%, silica bricks by 13% and high alumina bricks by 5%.
(4) Interaction with hydrocarbons
The hydrocarbons methane, ethane and natural gas, like CO, deposit carbon black in the presence of catalysts. They have a wider activation temperature range than carbon monoxide to precipitate carbon black, indicating the decomposition temperature of these hydrocarbons.
(5) “Oxidation-reduction” atmosphere
Carbon and silicon carbide refractory materials are oxidized at high temperatures in an oxidizing atmosphere. The carbon graphite brick medium has some slowdown in oxidation rate. The oxidation of silicon carbide refractory materials proceeds from the surface, and a SiO2 film is formed at the same time to prevent further oxidation. Due to the oxidation of the inner layer of carbonized carbon, the bricks will be damaged due to expansion during oxidation. Refractory bricks containing chromite are reduced at high temperatures in a reducing atmosphere. Magnesia-chromium and chromium-magnesite bricks are also reduced, and at temperatures exceeding 1600°C, there is a significant loss of strength and they become brittle.
(6)Interaction with sulfur dioxide gas
All types of magnesia bricks interact with sulfur dioxide gas SO2. MgSO4 is formed in the range of 400 to 900°C, and it decomposes at 1124°C. By further increasing the temperature, the periclase bricks are resintered by the activated form of magnesium oxide formed when the sulfide decomposes.
(7) Interaction with hydrogen
In aluminum silicate refractory materials, hydrogen is used to reduce oxides such as Na2O, TiO2, MgO, SiO2, etc. The hydrogen decomposes mullite to form corundum and silicon monoxide. In hydrogen medium, high alumina bricks and corundum bricks containing Al2O3≥85% have stable properties. Siliceous bricks are destroyed due to the rapid degradation of silica at 1200°C in a hydrogen medium.
(8) The corrosive effect of carbon monoxide
The most widespread and corrosive gas corrosive is carbon monoxide. Its corrosive effect lies in the reduction of refractory oxides and the precipitation of carbon black.
· [Abstract] Rotary kiln production and operation requires the use of refractory bricks as kiln lining, and low cement castables are commonly used as linings in the settling chamber. The lining treatment of the cone section depends on the situation. If the discharge opening is too small, no lining is required, otherwise low-cement castables are used and steel fibers are added to improve durability.
Zinc volatilization kilns all use rotary kilns for production and operation. The refractory bricks used for the kiln lining of the rotary kiln need to be made of consistent materials and accurate in size. Only then can the kiln body operate normally and the service life be extended.
Refractory Materials for the Settling Chamber
However, the kiln tail smoke chamber, which is the settlement chamber, is lined with clay bricks or low-cement refractory castables. Generally speaking, more low-cement castables are used, while clay bricks are rarely used as linings. The shape of the settling chamber is a cone, with the upper part larger and the lower part smaller, which facilitates the smooth discharge of smoke and dust. Because if this part is designed to be small, or the design of the unloading port is unreasonable, if it is too small, this part will be slapped during daily work to speed up the exhaust of smoke and dust.
At present, according to the situation of the manufacturers, some manufacturers basically do not do any lining treatment on the lower cone section of the settling chamber. The reason is that this area is often patted, and even the lining is patted off. It does nothing, but wastes the castables used and increases costs.
So, should this part be lined with cement refractory castables or bricks? In principle, it is still needed. Low cement castables are used as linings. If steel fibers are added to the castables in the cone section to increase the tensile effect, it will still have a certain effect. And if the discharge opening of the cone section is indeed too small, the use of low-cement castables as lining is indeed not very effective.
In short, whether this part is constructed with low cement castables or nothing is used depends entirely on the working conditions on-site. If the opening of the cone section is too small, there is no need for lining. If the unloading opening is of reasonable size, it is better to use low cement castable to cast the lining.
Rongsheng Refractory Materials Manufacturer has more than ten years of production and sales experience. It has its own unique insights into the design of refractory lining materials, thermal insulation, energy saving, and consumption reduction. We are committed to providing refractory lining solutions to extend the service life of refractory linings, thereby helping companies save production costs. We also have rich experience in various rotary kiln cases. Contact us for more solutions.
Research on new dry process cement rotary kiln mouth castables and analysis of the effects of various additives on its performance. Rongsheng Refractory Materials Manufacturer specializes in providing high-quality refractory lining materials for high-temperature industrial furnaces. Solve the problem of high-temperature industrial furnace linings, extend the service life of furnace linings, and save production costs for enterprises.
Refractory Castables for Cement Rotary Kiln Coal Injection Pipes and Corundum Silicon Carbide Castables for Front Kiln Entrance
Raw materials: special grade vanadium earth, Al2O3>85%; corundum, Al2O3>92%; calcium aluminate cement; α-Al2O3 powder; silica powder; sodium tripolyphosphate; silicon carbide particles and fine powder.
Basic formula: special grade bauxite, 5~8mm accounts for 12%, 3~5mm accounts for 23%, 1~3mm accounts for 15%, <1mm accounts for 20%. Corundum fine powder, SiC fine powder, and binder account for 30%.
Wear-Resistance Corundum Silicon Carbide Castable
(1)Amount of SiC.
The component of silicon carbide is SiC, which appears in colors such as green, black and yellow due to impurities. It is a covalently bonded compound with strong inter-atomic bonding force and has the characteristics of high melting point, high hardness, high strength and low expansion, high thermal conductivity, high electrical conductivity, and strong chemical properties.
(2) Amount of cement.
Cement is one of the important components of refractory castables. It is an important material that determines strength and also affects other properties. Different types of cement and their dosage have different effects on performance.
CA-80 cement refractory castable uses relatively pure CA-80 cement as a binding agent, and is mixed with corundum, mullite, special grade bauxite clinker and alumina powder and other bone powder materials or admixtures in proportion, and add water Made after mixing, shaping and curing. It is characterized by high refractoriness and load softening temperature, high high temperature strength, strong slag resistance and resistance to reducing gases.
(3)Amount of silica powder.
Microsilica powder is an aggregate of a large number of solid particles and belongs to the category of powder materials. Its properties mainly include particle size and distribution, particle shape, density, melting point and chemical composition, particle fluidity, filling, cohesion, consolidation and physical and chemical changes at high temperatures, etc.
In refractory castables, the basic mechanism of action of silica powder is filling. Improved workability, resulting in increased fluidity, increased volume, and reduced apparent porosity. Therefore, the strength of refractory castables has been significantly improved, and other high-temperature properties have also been greatly improved.
(4)Amount of gel powder.
Gel powder is a kind of retarder, used as an admixture for amorphous refractory materials. Refers to materials that increase mass by less than 5% and can improve the performance and workability of basic constituent materials as required. Its main function is to form complexes, inhibiting the hydration reaction and the formation of hydrates. That is, the positive ions dissociated from the retarder and the binding agent form a complex, which inhibits the formation of hydrates or the crystallization of the hydration reactants. Or it inhibits the growth of hydrate phase grains, thereby delaying condensation and hardening. The adsorption film is formed and the cement particles are wrapped, that is, the retarder is adsorbed on the surface of the cement particles and forms a film. It prevents cement particles from contacting water, inhibits cement hydrolysis and hydration reaction speed, and thus plays a retarding effect.
Effect of Various Components on the Performance of High Aluminum Castables
(1) Add SiC to high-aluminum castables to increase strength and wear resistance. Especially the high-temperature performance is enhanced.
(2) As the addition amount of silicon carbide increases, the normal and high-temperature strength of the castable increases first and then decreases. The appropriate addition amount of silicon carbide is 3%.
(3) Adding cement to high-aluminum castables can significantly increase its flexural and compressive strength and reduce its bulk density.
(4) Comprehensive analysis of the impact of cement blending on its physical properties shows that the best cement blending amount (w) is 5%.
(5) Different types of cement are mixed with different physical properties.
(6) Add silica powder to high-aluminum castables to significantly increase its strength.
(7) Comprehensive analysis of the impact of the blending of silica powder on its physical properties shows that the best blending amount (w) of silica powder is 4%.
(8) When different types of silica powder are incorporated, the changes in physical properties are related to the changes in SiO2 in the silica powder. The flexural strength and impact strength of materials with high SiO2 content are higher, the water absorption rate is correspondingly lower, and the volume and mass are larger.
(9) Add cement and silica powder to high-aluminum castables to significantly increase its strength.
(10) Comprehensive analysis of the impact of the blending of cement and silica powder on its physical properties shows that the best blending amount (w) of cement and silica powder is 5% + 2%.
(11) Using gel powder as a binding agent, the mechanical properties are significantly enhanced at high temperatures.
(12) As the content of gel powder increases, the normal and high-temperature strength of the castable first increases and then decreases. The appropriate additional amount of gel powder is 4% (w).
At present, corundum mullite bricks are one of the main products of blast furnace ceramic cups. Corundum-mullite bricks have some drawbacks in terms of performance. The main manifestation is that the product has serious missing edges and corners during the grinding and masonry process, which affects the masonry quality of the product. Corundum mullite bricks are only qualified when the quality qualification rate of corundum mullite bricks is guaranteed to increase by 2%. Rongsheng refractory material manufacturer‘s strict quality of corundum mullite bricks acceptance has won the recognition of customers. And promoting the sales of our refractory products to more than 100 countries around the world.
Rongsheng Corundum Mullite Brick for Sale
Analysis of the Causes of Missing Edges and Corners of Corundum Mullite Bricks During Grinding and Laying Process
Corundum mullite bricks have serious missing edges and corners during the grinding and laying process. Rongsheng Refractory Materials Manufacturer analyzes the reasons and summarizes them as follows.
Hardness. Hardness is generally considered an important indicator of a material’s wear resistance. The harder the material, the better its wear resistance, but in the case of large impact wear, the impact of hardness is not necessarily very large. Refractory bricks are heterogeneous and the hardness of each part may be different. For refractory bricks containing corundum and silicon carbide, if the bonding strength is sufficient, these high-hardness materials can still resist the wear of the refractory bricks after the low-hardness and easy-to-wear materials wear away.
Crystal structure and crystal solubility. Materials with a specific crystal structure have better wear resistance. For example, cobalt with a close-packed hexagonal structure has a small friction coefficient and is wear-resistant. Metallurgically speaking, metals with poor mutual solubility also have good wear resistance.
Strength. Refractory bricks will encounter a lot of impact wear during use. Therefore, high-strength refractory bricks have strong wear resistance.
Volume density. Refractory bricks with high volume density and low apparent porosity have strong wear resistance.
Temperature. Temperature affects the hardness, solubility and reactivity of materials, thus indirectly affecting the wear resistance of refractory bricks. Generally, as the temperature increases, the solubility and reactivity increase. Refractory bricks are used at high temperatures, and their wear resistance at high temperatures is very important.
Atmosphere. Similar to the effect of temperature, the atmosphere affects the mutual solubility and reactivity between materials, thereby affecting their wear resistance.
Corundum Mullite Bricks Directly from RS Factory
Technical key and project implementation content to improve the performance of corundum-mullite bricks
The product formula system is modified in a targeted manner based on the above factors. In the production process of this product, the density of the bricks is increased through reasonable particle gradation and the selection and use of high-quality aggregates. Optimize and increase the firing temperature to improve the physical and chemical properties and wear resistance of the product. Ensure the quality of the later grinding and masonry processing of the product, thereby ensuring the improvement of the quality of the pre-masonry of the product.
1) Use high-quality raw materials. Better quality alumina grade raw materials and brown corundum raw materials are used as aggregates. It ensures the high hardness of the material and increases the toughness of the refractory material without increasing the cost.
2) Increase the proportion of brown corundum fine powder and alumina fine powder in the matrix fine powder. Reduce the porosity of the product after firing and increase the density of the product.
3) Change the traditional product stacking method and add air inlets for kiln car stacking to make the firing temperature more uniform.
4) Increase the product sintering temperature so that the product is fully sintered and the internal materials are fully integrated and mutually soluble.
Implementation plan to improve the performance of corundum mullite bricks
⑴ Combined with the performance requirements of the product, select raw materials with higher density and hardness. It was finally decided to use a raw material combination of brown corundum and bauxite. Brown corundum acts as a skeleton in terms of hardness, providing high strength to the product. Bauxite is slightly inferior to brown corundum in terms of hardness, but it is tough and can wrap brown corundum at a slightly lower firing temperature. Use together to meet product performance and economic indicators.
⑵ Combined with the original formula structure, a small amount of bauxite is combined with brown corundum and then supplemented with mullite raw materials and alumina powder. The bricks are formed using high pressure to increase the density of the bricks and form a highly polymerized body. Change the traditional kiln coding method, increase the hand seam width, improve the temperature homogenization performance of the kiln car, and determine the appropriate firing temperature. The product can achieve the effect of mutual dissolution of raw materials, tight combination, and tiny pores inside the product.
Customized White Corundum Mullite Bricks from Rongsheng Manufacturer
Technical summary
In the first stage, the raw materials entering the factory are optimized. After inspecting various brown corundum raw materials and bauxite raw materials, and after research and discussion by the project team’s technical staff, it was finally decided to use Dengfeng’s brown corundum and Shanxi bauxite.
In the second stage, the formula ratio of the corundum-mullite product was further optimized, and the stacking method and firing temperature were determined through multiple experiments. The principle of close particle packing is used to adjust the proportion of aggregate and powder. At the same time, the ratio of brown corundum particles and alumina particles is adjusted in various proportions. It was finally decided to use a ratio of 2:1 to achieve a tight packing effect and also play a role in wrapping and soluble in each other. In the matrix fine powder, 2a% of alumina powder is added to increase the aluminum content and at the same time reduce pores. A 630-ton press is used for heavy-duty molding to increase the density of the bricks from 3.1 to 3.15. Relax the hand seams of kiln bricks and increase the width by 5mm. The kiln car fire channel is added to increase the firing temperature of the product by 40°C, so that the product is fully melted and the internal structure is dense.
In the third stage, multi-batch deployment plans are trial-produced, and a stable production plan is finally obtained.
Improved Performance of Corundum Mullite Bricks
Corundum mullite bricks use brown corundum combined with bauxite to enhance the wear resistance of the product. However, it has a certain impact on the high-temperature load softening temperature of the product, and the proportion of alumina is not easy to increase.
The amount of aluminum oxide powder added is controlled at 2a%, which is sufficient. Excessive alumina powder affects the firing temperature and also reduces the brick density.
In the matrix fine powder, it is advisable to reduce the addition of bauxite raw materials. The addition ratio can be reduced to 1a% to enhance the hardness of the matrix.
Rongsheng Refractory Materials Manufacturer is a powerful manufacturer of refractory materials production and sales. Our corundum mullite brick products have stable and reliable performance. Strict factory inspection. It extends the service life of the refractory lining of the customer’s industrial furnace and ensures the economic benefits of the customer’s production. Contact us to get free samples and quotes.
Why use zircon bricks for the construction of glass kilns? In the glass melting furnace, the molten glass liquid and the flame-flying material will cause certain erosion and damage to the zircon refractory bricks. refractory lining of the kiln, which in turn affects the service life of the glass-melting furnace. In addition, it is necessary to reduce the pollution of the molten glass.
Zircon Bricks for the Construction of Glass Kiln
From the performance indexes of representative zircon bricks for glass kilns at home and abroad, zircon bricks are more wear-resistant, more resistant to corrosion, and can reduce the pollution of molten glass. Zircon brick with such properties for glass kiln:1. High refractoriness and high softening temperature.2. anti-slag liquid erosion ability, strong acid resistance.3. High compressive strength.4. Good thermal shock resistance. The zircon brick is used for the working layer of the glass kiln wall, and its density is high, and it is strong against the glass liquid as the working layer of the pool wall. Therefore, the choice of zircon brick refractories for glass furnaces can extend the life of glass furnaces and improve the quality of glass. The zircon bricks used in the glass kiln are made of zircon as the main raw material, added with a binder and an additive, and are equipped in proportion, stirred, kneaded, formed, dried, and then fired at a high temperature. Zircon bricks with the zircon castables can work better in the glass kiln.
Zircon Bricks for Glass Kiln
What is the price of zircon bricks for a glass kiln? The price of zircon bricks on the market is currently not fixed. The actual price of zircon bricks for a glass kiln needs to consult the manufacturer, combined with the actual situation of the glass kiln, in order to get the most satisfactory products and quotations.
Performance of Sintered Zircon Brick for Glass Kilns
High temperature-resistant and corrosion-resistant zircon bricks are made of zircon as the main raw material, added with binders and additives, equipped in proportion, and fired at high temperature after mixing, mixing, molding, and drying. Also called sintered zircon brick.
Zircon bricks are divided into the high-density type and dense type according to production technology and physical and chemical indicators. RS Company Zircon Refractory Bricks for Sale, Sintered Zircon Brick for Glass Kilns, and Sintered Zircon Bricks for Glass Kilns are mainly used for the working layer of the wall of the glass kiln. Its density is high, and as a working layer of the pool wall, it has a strong ability to resist the corrosion of glass liquid. In recent years, the world’s glass industry melting furnaces have developed in the direction of large-scale and energy-saving.
Dense Zircon Brick with High Density and Low Porosity for Glass Kiln
The dense zircon brick with high density and low porosity is a special type suitable for the lining of the glass furnace melting pool for glass fiber melting. Generally, the production method of whole powder material, casting molding, and high-temperature firing are adopted. Performance of Dense Zircon Brick for Glass Kilns. 1. High refractoriness and high softening temperature. 2. Strong resistance to slag liquid erosion and strong acid resistance. 3. High compressive strength. 4. Good thermal shock resistance. Zircon Brick for Glass KilnsMethod for Improving Performance of Sintered Zircon Brick for Glass KilnsZircon bricks have high refractoriness and load softening point, low thermal expansion rate, and are not easily dissolved by chemical attack of molten slag. However its resistance to penetration (infiltration resistance) is poor, and the slag can penetrate into the brick through the pores. At the same time, it reacts with the decomposed zircon particles to form a metamorphic layer and collapse the brick structure. To improve the use effect of zircon bricks, the permeability of its slag must be reduced.
Dense Zircon Bricks
The improvement method is as follows: ① By adjusting the particle composition and changing the molding method, products with low porosity and air permeability are produced. However, products made by this method will inevitably reduce their thermal shock stability.②Add some additives to the bricks to increase the viscosity of the bricks and molten slag. High-purity zircon raw materials, a small number of high-efficiency additives, and suitable firing temperatures are the key factors for making high-density zircon bricks. The introduction of additives can not only ensure that the product can be fully sintered at a temperature far lower than the decomposition temperature of zircon but also reduce the reactivity, wettability, and permeability between the molten glass and the brick to varying degrees. Clay combined with zircon bricks, the type and amount of clay used greatly affect the properties of the bricks. The addition of clay will reduce the refractoriness of the product because Al2O3 has a solvent effect on zircon. In the ZrO2-Al2O3-SiO2 ternary system, when the composition is ZrSiO4 15%, Al2O3 15%, and SiO2 70%, a eutectic liquid phase is formed, and its melting point is 1610℃.
As the firing temperature increases, the apparent porosity of the clay-combined zirconite brick decreases, the air permeability increases, the number of coarse pores increases, the compressive strength and high-temperature flexural strength increase, and the corrosion resistance of the product increases. At the same time, the thickness of the impregnated layer increases. When the binding clay is not added, the proportion of the fine zircon powder is changed, and the test result of sintering at 1500 ℃ shows. As the amount of zircon fine powder increases, the air permeability decreases, the number of fine pores increases, and the corrosion resistance of the product becomes better. When the amount of zircon fine powder is 60%, the thickness of the impregnated layer is the thinnest. It can be seen from the above analysis that to adjust the corrosion resistance of the product, reduce the air permeability, improve the pore distribution, and obtain a zircon product with strong resistance to penetration. In the process, it is necessary to consider adopting a suitable firing temperature, adding an appropriate amount of fine zircon powder, and using a small amount of bonding clay.
What are the Refractory Bricks for the Lining of the Glass Kilns? The lining of the glass kiln is subject to chemical erosion, mechanical erosion, and large temperature fluctuations, and the refractory materials used for the glass kiln lining are like…Contact RS Refractory Company for a Free Quote. Glass is mainly made by using silica sand and soda ash as raw materials through high-temperature melting. A Glass melting furnace is thermal equipment for melting glass, usually made of refractory bricks.
Fused AZS Refractory Bricks for Glass Furnaces
Refractory Materials for Glass Furnaces
Glass melting furnaces can be divided into two categories: pool kilns and crucible kilns. According to the operation mode, it is divided into continuous operation furnaces and intermittent operation furnaces. According to the heating method, it can be divided into the flame kiln and electric heating kiln. So, how should refractory bricks be used in glass kilns? Perhaps manufacturers of refractory materials for glass kilns will answer such questions for us. Refractory Bricks Used for Glass Kiln. Because refractory bricks are widely used, from low temperature to medium temperature to high temperature, it is a necessity for the construction of the lining structure of industrial kilns.
When we choose refractory materials, we must consider many aspects. How to choose our applicable refractory brick products. First, we need to see which type of brick we need. Refractory bricks have different brick types and different uses. Secondly, we must see which kind of furnace is used and then the quality of refractory bricks. When determining the demand, the quality of the refractory bricks meets the standard and then compares the prices. Selection of refractory bricks for glass kiln is the most common type of kiln used in the glass industry. It is made of refractory bricks. There are flame-type pool kilns and electric-heated pool kilns.
The crucible kiln is to put the glass batch materials into the crucible, and then put them in the kiln to heat them together and then pour them into glass products after the materials are melted. The characteristic of this kiln is that the molten glass does not directly contact the kiln lining and the crucible is generally made of high-alumina refractory bricks and clay refractory bricks. The damage to the lining of the glass melting furnace is mainly chemical erosion and has the effect of thermal stress. The degree and speed of chemical attack are closely related to the location of use, the temperature of the furnace, and the type of molten glass. Of course, the quality of the lining itself is also very important. When choosing refractory bricks for glass melting furnaces (https://www.hy-refractory.com/service/product_knowledge/glass-tank-furnace-refractories.html), consideration should be given to the type of furnace, the location of its use, and its damage mechanism, the type of melting glass, and the type of fuel.
Fused AZS Bricks for Glass Kiln
Fused Zirconia Corundum Bricks for Glass Kilns
Fused Zirconia Corundum Bricks. Categories Refractory Bricks. WikiTags: Lining of the Glass Kilns, Refractory Bricks. At present, fused zirconia corundum bricks and corundum bricks are widely used at home and abroad at the wall and bottom of the glass kiln in contact with the molten glass. The lower layer of the melting pool is built with clay refractory bricks. What are the precautions when using clay refractory bricks in the glass kiln? Clay refractory bricks are commonly used refractory bricks in blast furnaces, hot blast stoves, heating furnaces, ceramics, and refractory brick firing kilns. In order to achieve the best results, we need to pay attention to the following matters when used in a glass furnace.
Large Fireclay Refractory Bricks for Glass Kiln
Large Fireclay Bricks for the Glass Kilns
Large Fireclay Bricks for the Glass Kilns. 1. Clay refractory bricks cannot bear weight or be compressed when used at high temperatures. Therefore, it can only be used on the lower part of the pool wall or at a lower temperature at the bottom of the pool. 2. The gap between refractory bricks is controlled within 1.5mm~2mm. 3. The inside of the kiln shell should be flat without unevenness, let alone tilted.4. When using refractory bricks, clean the dust and slag scraps on the inner wall of the kiln shell to avoid loosening. 5. Leave a little expansion joint between the refractory bricks. 6. Bond clay refractory bricks with special cement for refractory bricks. 7. The lining of important parts and parts with complex shapes should be pre-laid first. 8. The lock seam should be firm. When processing bricks, bricks should be finely processed with a brick cutter, and manual processing of bricks should not be used. The capped bricks in the rotary kiln and under the brick slabs should not be less than 70% of the original bricks. In flat joint bricks and curved bricks, it shall not be less than 1/2 of the original bricks. It must be locked with original bricks. The processing surface of the brick should not face the inner side of the furnace. 9. Clay refractory bricks must be stored in a dry warehouse. Having mastered the selection techniques and methods of these refractory brick materials for glass kilns, I believe you will easily find the refractory bricks for glass kilns that best suit your production needs. For more information, please stay tuned to this blog.
And also the Insulating Fire Bricks Used for Kiln Linings. Insulating Fire Bricks of different materials, when used for kiln linings, can increase the heat storage function of industrial kilns and reduce the loss of energy… Contact Rongsheng for Free Quote of Refractory Bricks Categories.
RS Cement Kiln Lining Refractory Bricks for Sale. Commonly used refractory bricks in cement kilns include low-temperature and alkali-resistant bricks, and high-temperature and high-temperature Silicon Carbide Mullite Bricks. Cement Kiln Lining Refractory Bricks … For Free Quote at inquiry@global-refractory.com.
Alkaline Refractory Bricks for Cement Kilns
Why Use Alkaline Refractory Bricks for Precalcined Cement Kilns? During the calcination process of the pre-calcining kiln clinker, a large amount of melt (liquid phase) appears in the kiln material from the back end of the upper transition zone. Some ingredients in the kiln material are calcined in the melt-through of the raw maturation material until it is out of the kiln. Within this range, alkaline refractory bricks that withstand high temperatures can meet their process performance requirements. The masonry length of alkaline refractory bricks is about (6~10)D of the kiln diameter, which is also the most severely damaged part of the lining brick. The use of the lining brick in this part directly affects the operation rate of the kiln. Therefore, the technological progress product performance, and output status of basic refractory bricks are paid attention to by people.
Alkali Resistant Bricks for Rotary Kilns
Magnesia Chrome Bricks for Cement Kiln
At present, the alkaline refractory bricks used in the pre-calcining kiln are mainly spinel magnesia bricks that directly join magnesia-chrome bricks and magnesia-aluminum bricks. This article mainly introduces the direct bonding of magnesia-chrome bricks. Directly Bonded Magnesia-Chrome Brick, Brief Introduction of Directly Bonded Magnesia-Chrome Brick for Cement Kilns. Magnesia-chrome bricks appeared in the 1930s. At that time, the performance of silicate-combined magnesia-chrome bricks (common magnesia-chrome) was still relatively poor and was used in traditional rotary kilns. Beginning in the 1960s, there have been direct-joined magnesia chrome bricks (straight magnesia bricks) with better performance.
Due to the high-temperature resistance, melt erosion resistance, redox resistance, mechanical stress resistance, and excellent kiln hanging performance of straight magnesia bricks, after being put into use, it is widely used in the transition zone and firing zone of the preheater kiln. Become the mainstream. In the 1980s, the output and diameter of the pre-calcining kiln were further expanded. In addition, due to the rapid increase in crude oil prices, coal with high ash content and petroleum coke with high sulfur content gradually replaced fuel oil. The high content of alkali sulfur makes the straight magnesia bricks in the upper and lower transition zones of the kiln vulnerable to damage and shortens the service life.
As a result, magnesia-aluminum spinel bricks with strong alkali-sulfur corrosion resistance have been used in the upper and lower transition zones of some large-scale pre-calcining kilns. At this point, the dominance of magnesia bricks began to break. In the late 1980s, some industrialized countries further emphasized the problem of chromium pollution, that is, when magnesia-chrome bricks are used in cement kilns, Cr3+ is transformed into Cr6+ which is harmful to the environment and the human body. Industrialized countries have formulated a series of regulations on environmental protection, sanitation, and cement-related ingredients. Fully monitor the residual bricks of cement kiln magnesia-chrome bricks, the drainage of cement plants, and the chromium content of cement products. In the 1990s, some cement companies in industrialized countries used relatively cheap industrial waste as raw material fuel due to environmental protection needs. Increased the alkali sulfur’s erosion of kiln lining materials, and put forward more demanding requirements for alkali refractories.
Magnesia Chrome Bricks for Cement Kilns
To promote the further optimization of magnesia-chrome bricks, super-direct bonded magnesia-chrome bricks with better performance have appeared in the pre-calcining kilns with more severe working conditions. On the other hand, the process of chromium-free alkaline bricks is accelerated to further improve and improve technology. In the 21st century, chromium-free alkaline bricks have completely replaced magnesia-chrome bricks in some industrialized countries and have better performance than magnesia-chrome bricks. It is specifically reflected in the development trend of the further increase in the operation rate of the pre-calciner kiln and the further decrease in brick consumption. In my country, in 2014, the Ministry of Environmental Protection formulated the solid waste production cement pollution control standard, which specified the limit of the pollutant content in cement products, Cr6+, to be 0.05mg/L. Its value is close to that of industrialized countries. It can be said with certainty that the limit value will definitely become stricter over time.
Although restricted by environmental protection regulations, magnesia-chrome bricks are still used by some cement plants due to their excellent kiln-hanging properties and relatively low prices. They are the most consumed variety in cement production. But the general trend is to decline year by year. At present, some people of insight in my country’s cement industry have raised the issue of chromium pollution in some conferences and articles, which has attracted the attention of relevant leaders.At the same time, some design units have reduced or stopped using magnesia-chrome bricks in their drawings. Some large domestic cement groups and foreign-funded enterprises have partially or completely stopped using magnesia-chrome bricks. The above situation greatly reduces the usage of magnesia-chrome bricks. In addition, the fuel used in some areas contains high sulfur content, which intensifies the chemical erosion of magnesia-chrome bricks, forcing companies to reduce or stop using them.
As the country further strengthens the environmental protection of water resources and controls the chromium content in cement. The regulation on the limit value of hexavalent chromium in magnesia-chrome brick residual bricks will be strict with time. In the end, forcing magnesia-chrome bricks to withdraw from the cement kiln, manufacturers that produce magnesia-chrome bricks must arouse great attention. Rongsheng Refractory Manufacturer provides high-quality refractory materials for cement kilns. Including direct bonding of magnesia chrome bricks, magnesia spinel bricks, and various wear-resistant castables. For more information about alkaline refractory bricks, please visit our website: https://rongshengrefractory.com/several-kinds-of-alkaline-refractory-bricks/.
Refractory Materials for Cement Rotary Kilns
Cement Kiln Lining Refractory Bricks Refractory Bricks for Cement Kiln
For the firing zone of the cement rotary kiln, a stable and strong kiln skin is required. Because it can protect the refractory lining and reduce the heat loss through the kiln body. A few centimeters of stable kiln skin can not only extend the life of the lining material by nearly 100% but also reduce the temperature of the kiln body by several hundred degrees. This means reducing heat loss by up to 25%.
When the local kiln appears thick skin, it is known as “ring formation.” It will hinder the operation of the kiln considerably. The most serious is that it has built an unfixed cross-section of the kiln, which hinders the steady flow of materials and fuel gas into the kiln. Once the kiln skin is looped, it cannot fall off by itself, and the kiln has to be stopped in order to deal with it. Rotary Kiln in the Cement PlantThe rate of kiln shutdown due to loop formation accounted for 80%. The change cycle ranges from once a month to more than once a week. It is for this reason that people have been studying methods to prevent or deal with kiln skin loops that hinder operation.
Therefore, it is considered whether it can be prevented by selecting suitable refractory materials, or at least the occurrence of ring formation can be reduced. Classification and Location of Kiln Skins and Ring Formation. According to the material flow, the kiln skin and ring formation in the preheater, rotary kiln, and cooler are divided into different types. According to these classifications, the raw material loop occurs in the decomposition zone where the material temperature is between 800°C and 1200°C. The sintering ring occurs at the front end of the firing zone where the material temperature is 1200~1350℃.
The clinker ring occurs at the end of the firing zone where the material temperature is 1200~1400℃. Another obstacle to the formation of kiln skins is the slurry ring on the wet long kiln. The skin on the suspension preheater and decomposition belt of the rotary short kiln, and the well-known “clinker mushroom tumor” on the cooler inlet chute. Refractory Material Affects the Possibility and Limit of Ring FormationThe chemical atmosphere in the kiln and the normal operating conditions affect the desired formation of the kiln skin and cause the trouble of material ring formation. However, refractory materials can also affect the stability of the kiln skin due to their different bonding strength. Experiments have shown that dolomite bricks have the strongest bonding force, followed by magnesia-chrome bricks and direct-bonded magnesia-chrome bricks (MgO content 60~70%), and magnesia spinel bricks (Almag 85) are the weakest.
Magnesia Aluminum Spinel Bricks for Cement Kilns
Magnesia Spinel Bricks for Cement Kilns
Magnesia Spinel Bricks Manufacturer. The “Mineral-Chemistry” study confirmed that the bonding force at the interface between the kiln skin and different bricks was measured by the mineral composition of the “kiln skin-brick” interface and the liquid “wetting” angle. Therefore, a layer of C3S enrichment zone with high refractoriness is formed on the interface between kiln skin and brick. This layer of C3S also contains tricalcium aluminate and ferrite phases. If the temperature drops below the stability limit of C3S (1250°C), C3S usually decomposes into C2S and secondary free CaO. But obviously, the incorporation of foreign ions, such as MgO, will stabilize C3S. Due to the decrease of the local CaO/SiO2 ratio in the area close to the surface of the brick, a C2S-rich boundary layer is formed, which results in a lower bonding force on the magnesia-chrome brick. In the presence of Cr2O3, C2S is partially stabilized.
However, if the interface temperature drops, that is, if the kiln skin becomes thicker, β-C2S will be converted to γ-C2S, with a volume expansion of 10%, resulting in “pulverization” and weakening of the binding force of the ring to the lining. So that the knot loops fall off. Magnesia spinel bricks have a particularly strong “chalking” effect. Although a C2S-rich layer is formed, the liquid phase obviously does not infiltrate the bricks to such an extent. On the other hand, there is no adequate amount of ions that can stabilize β-C2S. If the temperature drops in the contact zone, it is easier to form γ-C2S, so that the ring of materials will fall off. Because the magnesia spinel brick has a higher control of Fe2O3 content, it will not generate a C2S layer enriched with iron-free aluminate. The situation of magnesia chrome brick is the opposite because it contains higher Fe2O3.
Based on the previous observations, it is clear that magnesia spinel bricks can cause the ring to fall off, or prevent the formation of a C2S-rich ring layer that hinders operation. These loops mainly occur before and after the decomposition zone and the firing zone. Lining with magnesium spinel bricks can also prevent the formation of “clinker mushroom tumors” at the inlet chute of the cooler. As to whether the magnesia spinel brick can successfully eliminate the problem of skinning containing potassium sulfate, potassium carbonate, silica calcite, alkali metal sulfate, and alkali metal chloride, it is still worth discussing.
The looping of slurry in the cyclone, short dry kiln flue chamber, long wet kiln, and skin on the wall and top of the hot gas chamber of the grate preheater are all such problems. Obviously, the lining made of Almag85 grade magnesia spinel bricks shows that it can effectively prevent the formation of clinker rings, sintered rings, and raw material rings. Learn more about the magnesia alumina spinel bricks from Rongsheng Refractory Manufacturer.
The ignition and baking of the glass kiln are based on the physical and chemical properties of the refractory materials used in the kiln, that is the thermal expansion properties of the refractory materials. After heating and baking, the refractory material completes the internal crystal transformation and volume change, so that it can be used normally at high temperatures.
In the past, AZS bricks were expensive. Therefore, the kiln is not used or only used in small quantities in key parts. In the past two decades, with the development of high-efficiency and energy-saving kiln technology, AZS bricks have been widely used. AZS is increasingly used not only for the pool walls that are in contact with the glass liquid but also for the flame space. Due to the influence of traditional inertial thinking, most glass factories currently only consider the thermal expansion of silica bricks when baking kilns, but do not pay attention to the thermal expansion of AZS bricks. Therefore, fracture problems of AZS bricks often occur before and after the kiln is put into operation, which directly affects the life of the kiln.
Glass Kiln AZS Refractory Bricks
Thermal Expansion Characteristics of AZS Bricks
AZS brick contains a certain amount of ZrO2, which is a homogeneous polycrystalline. That is, the same chemical composition can form three types of crystals with different structures and properties due to different temperature conditions. There are three types: monoclinic ZrO2, tetragonal ZrO2, and cubic ZrO2.
Changes in the crystal system are often accompanied by changes in volume. Taking 33# AZS as an example, it was found through experiments that when the temperature range is 0-1100°C, the bricks gradually expand as the temperature rises. When the temperature range is 1100-1200℃, the bricks shrink violently as the temperature rises. The linear expansion rate dropped from about 0.8% to about 0.6%, which is what is usually called abnormal expansion. This is caused by the transformation of the ZrO2 monoclinic system into the ZrO2 tetragonal system. When the temperature is higher than 1200°C, the bricks begin to expand again as the temperature rises.
It can be seen from laboratory testing data that the overall expansion is not large below about 1600°C.
Precautions when Baking the Glass Kiln
The kiln has a fire-amplification stage. The fire in the hot-air kiln is generally 900-1000℃. The practice has proved that most of the fractures of AZS bricks occur after a fire. The reason is that the temperature rise rate is too fast during the 1100-1200°C period when monoclinic ZrO2 transforms into tetragonal ZrO2. Therefore, it is generally required that the speed does not exceed 15°C/hour. Many manufacturers control it at 5°C/hour, and the speed does not exceed 15°C/hour in other temperature ranges. In this way, the AZS bricks have sufficient time to undergo crystal transformation and avoid fracture.
There is a temperature difference of several hundred degrees between the flame contact surface and the non-contact flame surface during the kiln baking process. In order for the outside of the brick to be able to undergo crystalline transformation safely, it is necessary to maintain a low heating rate within a larger temperature range. Therefore, the temperature range in the kiln is usually expanded from the theoretical 1100-1200℃ to about 1100-1350℃.
The upper 300-400 mm of the pool wall bricks are not insulated during normal production and need to be cooled. To reduce the temperature difference between the inside and outside of the kiln, insulation materials such as aluminum silicate fiber should be used for temporary insulation to prevent brick breakage. When the temperature reaches above 1500°C, the insulation fiber can be taken out.
When cooling the pool wall tiles, the cooling air inlet should be opened gradually. Generally, it is opened 5 times, and 20% is opened every hour.
The quality of the kiln’s work is related to the life of the kiln. Therefore, it is extremely important to correctly grasp the expansion performance of fused zirconium corundum bricks, standardize it in the kiln heating curve, and implement it carefully. Rongsheng refractory material manufacturer can provide a comprehensive range of lining bricks for glass kilns, including silica bricks, corundum bricks, corundum mullite bricks, AZS bricks, etc. Feel free to contact us for details.
High-temperature-resistant inorganic adhesives have been widely used in the heat-resistant bonding of metals, ceramics, graphite, oxides, and other materials. Easy to use, used for direct bonding of high-temperature resistant materials. The coating can be sprayed directly on the surface of a high-temperature substrate of 400-1000°C. When the water evaporates, the coating will instantly adhere to the surface of the substrate, forming a uniform and dense high-temperature resistant protective coating with good thermal shock resistance.
High-Temperature Gunning Refractory Material for Lining Repair
It also has good strength at high temperatures, with an average compressive strength of 90Mpa and a tensile strength of 8Mpa at 1300°C. After applying high-temperature inorganic adhesive on the kiln windshield, hanging parts, and cracks, the bond will be firm and will not cause any damage to the kiln lining. Adhesives are easy to use and play a very important role in the normal operation of the furnace. It has been successfully used in rotary kilns, drying furnaces, and combustion chambers in the cement industry. Heating furnaces and smelting furnaces in the machinery industry. Electric furnaces, roasters, and blast furnaces in the metallurgical and chemical industries. Tunnel kilns in the ceramic industry, boilers in the thermal power industry, and other types of kilns.
The high-temperature-resistant expansion glue uses a high-temperature inorganic silicate modified solution as the film-forming material, and is composed of rare earth oxides, re-expanded mullite, and vaporized SiO2 powder as fillers. The cured coating film has a temperature resistance of up to 2200°C and can maintain good thermal stability, bonding performance, wear resistance, and corrosion resistance in high-temperature environments. The coating has a high linear expansion coefficient, and the coating expansion rate can reach 15% under high-temperature conditions.
The kiln lining protective coating uses the company’s special high-temperature resistant inorganic silicate modified solution as the film-forming substance and is composed of nano-scale alumina, silicon carbide, rare earth oxides, ceramic fibers, etc. The cured coating film has high-temperature resistance, which can reach 1800°C, thermal shock resistance, high adhesion, good heat insulation, strong aging resistance, and convenient construction. It can be sprayed directly on the surface of various materials lining the kiln, including insulation bricks, castables, metals, ceramics, refractory fibers, quartz sand, silicon carbide, quartz glass, etc.
