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Improvement of Lime Kiln Burner Brick Material

2024-09-142024-09-13 by globalrefractory

The magnesia refractory bricks used in the burners of general sleeve lime kilns are prone to breakage within more than one year of use. This makes the service life of the burner bricks inconsistent with the life of the kiln body. One-third of the burner bricks of the sleeve lime kiln broke within less than one year of use, while the service life of the lime kiln is more than 3 years. Therefore, the service life of the burner bricks is inconsistent with the life of the kiln body. Although the breakage of the burner bricks does not affect the use of the lime kiln, it has a certain negative impact on the calcination process.

The Reason Why Burner Bricks are Easy to Break

The reason why burner bricks are easy to break is that the material used for burner bricks is magnesia refractory bricks. In addition to having excellent high temperature resistance and anti-lime reactivity, this alkaline material has the following unfavorable factors, which lead to premature breakage.

1: Magnesium refractory materials have large thermal expansion and poor thermal shock resistance. The burner bricks are washed by the hot air flow of the flame, and the thermal shock environment they endure is harsh, which makes them prone to cracks caused by thermal shock.
2: Due to the large thermal expansion coefficient, the thermal stress of magnesium refractory materials is high. When there is local stress concentration, it is easy to break.
3: Magnesium refractory materials are easy to hydrate, resulting in bulging and cracking. They are greatly affected by environmental conditions during construction. Improper baking is also prone to cracking, resulting in falling blocks. In cold and humid weather, the moisture in the fire mud is not easy to remove, and it is easier for the bricks to hydrate. Therefore, the construction environment conditions and baking requirements are strict
4: Magnesium refractory materials have low hot strength and are prone to creep under thermal stress.

Corundum-Mullite Burner Brick

Improvement of burner brick material The choice of corundum-mullite refractory castables to make burner brick prefabricated parts has the following advantages:

1: The main crystal phases of corundum-mullite refractory castables are corundum and mullite. The former has a high melting point of 2050℃, hardness and strength, can resist high temperature and airflow erosion, and has excellent high temperature wear resistance. The melting point of mullite is also relatively high at 1840℃, and its characteristic is a small thermal expansion coefficient. The crystal has a needle-column mosaic structure and has good thermal shock resistance. The composite refractory castable of corundum phase and mullite phase has the advantages of both, which can effectively resist the erosion of burner bricks by flame hot air flow. It can withstand harsh thermal shock environments and prevent burner bricks from breaking.
2: There is no hydration problem with corundum mullite refractory castables, and the construction is less affected by the environment. The construction conditions are not demanding, and the pouring, curing and heat treatment can be carried out at the material supplier, so the quality is easy to be guaranteed. It will not hydrate and crack during construction and baking.
3: The burner brick is a special-shaped brick, which is not easy to be machine-pressed. The pouring method is easy to achieve integral or split forming, and realize precise control of shape and size. The critical particle size of machine-pressed bricks is limited, generally 5 mm, while the critical particle size of castables can be as large as about 20 mm, which is conducive to the stability of the structure and improves the resistance to thermal shock.
4: When the burner brick is in use, the gas (or fuel oil) is sprayed into the furnace, and the CaO dust in the furnace is not easy to adhere to the burner cavity, and the reaction of CaO and Al2O3-SiO2 materials will not occur. Even if a small amount of CaO adheres to the burner brick, the Al2O3 content in the burner brick is high (greater than 75%), while the content of SiO2 and CaO is relatively low. According to the A12O3-SiO2-CaO ternary phase diagram, the temperature of the reaction is about 1500℃. It can be considered that the solid phase reaction of Al2O3-SiO2-CaO is not easy to occur at the working temperature of the lime kiln.

The magnesia refractory bricks used in the burners of general sleeve lime kilns are prone to fracture after more than a year of use, which makes the service life of the burner bricks out of sync with the life of the kiln body. That is, the burner of the sleeve kiln is prone to fracture. By analyzing the cause and reproducing the prefabricated burner bricks made of corundum mullite refractory castables suitable for the burner of the sleeve kiln according to the combustion process of the lime kiln calcining zone and the structure of the lining refractory material, the problem of burner brick fracture is effectively solved. And practice shows that the service life of the corundum mullite burner bricks is synchronized with the life of the kiln body.

Performance of High-Purity Mullite Refractory Bricks for Lime Kilns

High-purity mullite refractory bricks for lime kilns have important application value in the field of refractory materials. High-purity mullite refractory bricks for lime kilns are a type of refractory material specifically used in the lime kiln industry. It is made of high-purity mullite as the main raw material and sintered at high temperature. High-purity mullite refractory bricks for lime kilns have good wear resistance, high temperature resistance, shock resistance and corrosion resistance, and are an indispensable and important material in lime kiln production.

First of all, lime kiln high purity mullite refractory bricks have excellent refractory performance. This refractory performance advantage ensures the reliability of lime kiln high purity mullite refractory bricks during long-term use.
Secondly, lime kiln high purity mullite refractory bricks have excellent wear resistance. High purity mullite refractory bricks have high hardness and wear resistance, which can effectively resist the wear of materials and extend service life.
Next, lime kiln high purity mullite refractory bricks also have good seismic resistance. Lime kiln high purity mullite refractory bricks have good seismic resistance, which can effectively resist the influence of vibration on its structure and performance, and ensure long-term stable operation of equipment.
In addition, lime kiln high purity mullite refractory bricks also have good corrosion resistance. Lime kiln high purity mullite refractory bricks can resist the erosion of chemical substances and maintain their stable performance.

In short, lime kiln high purity mullite refractory bricks have excellent refractory performance, wear resistance, seismic resistance and corrosion resistance. Suitable for the production environment of various types of lime kilns. Its application can improve the working efficiency of the lime kiln, extend the life of the equipment, and reduce production costs. It is an indispensable and important material in the lime kiln industry.

Lightly-Burned Dolomite Double Chamber Kiln (Double C Structure) Kiln Refractory Lining Material

2024-09-142024-08-30 by globalrefractory

Double-chamber kiln is widely used in the production of metallurgical lime due to its advantages such as low heat consumption, high degree of automation, easy-to-adjust production, parallel flow heat storage, less refractory material usage, less floor space, stable product quality, etc. A project uses this kiln to produce and supply light-burned dolomite. Rongsheng Refractory Material Manufacturer supplies refractory lining materials for double-chamber kiln double C structure kiln of light-burned dolomite.

Double-Chamber Kiln Refractory Lining Structure

The construction of a double-chamber kiln of a light-burned dolomite manufacturer adopts a domestic double-chamber kiln with a “double C structure”. Its internal refractory masonry structure is shown in Figure 1. The double-chamber kiln lining structure is divided into cooling zone, calcining zone, and preheating zone from bottom to top. They are built with refractory materials with good high-temperature resistance, wear resistance, and thermal insulation performance. The two kiln chambers are constructed with an intermediate channel and 8 cooling pillars. The outer ring bricklayer of the kiln is counted from the bottom of the kiln chamber, a total of 194 layers.

Figure 1 Refractory masonry structure inside double-chamber kiln

The cooling belt and the bottom of the steel structure are leveled with low cement castables, and then the cooling belt is laid. From the 1st to the 40th floor, from the steel shell structure outward, coating material, two layers of fiberboard, insulation bricks, and high-strength clay bricks are used in sequence. The thickness of the fiberboard is 30mm, the thickness of the insulation brick is 230mm, and the thickness of the high-strength clay brick is 260mm. When laying each layer of bricks, expansion joints are reserved in the circular ring of the kiln brick layer at a certain distance.

From the 41st to the 82nd floor, as the kiln height gradually approaches the calcining zone area, the working temperature increases accordingly, and the brick lining working layer is changed to high-alumina refractory bricks.

The middle channel is equipped with a fire door. It is used to observe the ash accumulation during the kiln shutdown, and a template is required during masonry.

The calcining zone has the highest temperature, which can reach 1100℃. Considering the calcination characteristics and temperature, the working layer of the 83rd to 161st layers of bricks on the outer ring of the kiln is built with mullite refractory bricks. From the steel shell structure to the outside, it is built with coating material, two layers of fiberboard, insulation bricks, and mullite bricks in sequence.

Anchors are welded on the bottom of the steel structure and the supporting structure inside the kiln, and castables are used for masonry. At the same time, thermocouples are evenly arranged in the inner and outer ring areas of each kiln chamber to detect the calcination of the kiln.

The 162nd to 194th brick lining working layer is built with high-strength clay bricks as part of the preheating zone.

The entire kiln structure should be strictly symmetrical. In order to ensure the construction period, the masonry of the two kiln chambers can be carried out at the same time. During the masonry process, overlapping of brick joints should be avoided, and the mortar should be applied in sufficient and uniform amounts.

Problems with the Lining of the Double-C Structure Lime Kiln

After the double C structure lime kiln was in production for a period of time, two high-temperature spots were found on the surface of the furnace shell, and it was forced to be emptied for inspection. It was found that the refractory bricks in the working layer at about 700mm from the bottom of the kiln spray gun were burned, and the refractory bricks in the insulation layer were molten (see Figure 2). In order to avoid the recurrence of this phenomenon, it is necessary to analyze the cause of the burning of refractory bricks. The project team conducted a comprehensive analysis of the aspects of design, process operation, raw material structure, equipment installation structure, etc. Find the cause and optimize and rectify it.

Figure 2 Burning condition of refractory material in kiln shell at high-temperature point — Figure 2 Burning condition of refractory material in kiln shell at a high-temperature point

After investigation and inspection, it was found that the coal powder spraying gun was not installed correctly, and the flame directly washed the furnace wall, which was the direct cause of the burning of the refractory materials. The coal powder conveying fan was not a variable frequency fan, the wind pressure was too high, and the flow rate was too fast. The coal powder guide pipe was worn in less than one month, and the coal powder conveying of the spray gun increased, which was another reason for the aggravation of the burning of the refractory materials.

Rectification of the Lining of the Double-C Structure Lime Kiln

The construction and maintenance team was required to strictly follow the drawings to ensure that the spray gun was vertically parallel and downward and to ensure the distance between the spray gun and the furnace wall. This reduced the burning of refractory materials.

At the same time, the pulverized coal conveying fan was retrofitted with frequency conversion, and the fan operation program was updated. That is, the fan operating frequency was reduced during the reversing period, and the fan speed was adjusted according to the kiln conditions during the combustion period. This ensured the transportation of pulverized coal while reducing power consumption. The double-chamber kiln after the rectification had a good operating effect, and no corresponding refractory material burning occurred.

How to Improve the Service Life of the Kiln Refractory Lining?

After the double C structure kiln refractory bricks were overhauled and the conveying fan frequency conversion was modified, the entire kiln no longer had refractory material burning. This fully proves that the rectification effect is good.

(1) The abnormal damage of the furnace wall in the high-temperature section of the lime kiln causes the furnace shell to turn red. The main reason is that the mullite bricks in the working layer are corroded and melted at high temperatures during the production process.
(2) Alkali metals such as K₂O and Na₂O react with mullite bricks at high temperatures to form low-melting products such as feldspar. The mullite bricks are continuously corroded, and the furnace wall becomes thinner after melting, which causes the furnace shell to turn red at high temperatures.
(3) The source of alkali metal oxides in the lime kiln is mainly the ash of the mixed coal. Due to the double C structure of the kiln type, abnormal installation of the spray gun will also cause ash to adhere near the end wall and corrode the furnace wall.
(4) The frequency conversion of the conveying fan is conducive to reducing power consumption, stabilizing the kiln condition, reducing the erosion of the coal powder guide pipe, and increasing its service life.

Rongsheng Refractory Material Production and Sales Manufacturers is a powerful refractory material production and sales manufacturer. Rongsheng Refractory Manufacturer can customize the construction and maintenance plan of refractory lining according to the actual working conditions of high-temperature industrial furnaces. For high-quality refractory bricks and amorphous refractory products, contact us for free samples and quotes.

Advantages of Tunnel Kiln Lightweight Mullite Bricks Hang Roof Bricks

2024-08-02 by globalrefractory

Hanging roof tiles are generally made of mullite, so they are often called Mullite Hang Roof Bricks, or roof anchor bricks. The composition of mullite hanging bricks and mullite lightweight bricks is similar, and the general alumina content is between 65% and 75%. In addition to mullite, the mineral composition contains low alumina and a small amount of glass phase and cristobalite. Those with higher alumina content also contain a small amount of corundum.

Characteristics of Hang Roof Bricks

Low thermal conductivity and good thermal insulation effect.
Low heat capacity. RS insulation bricks store very little heat energy and have obvious energy-saving effects during intermittent operation.
Low impurity content, with very low oxide content such as iron and alkali metals. Therefore, the refractoriness is high, and the high aluminum content allows it to maintain good performance under reducing atmosphere.
High hot compressive strength.
Standard appearance and dimensions. Speeding up the masonry construction and reducing the amount of refractory slurry ensures the strength and stability of the masonry.

Lightweight Mullite Bricks Hang Roof Bricks

Performance Indicators of Hang Roof Brick Mullite

Fire resistance temperature: 1350-1550. Volume density: 800-1000kg/m3. Thermal conductivity (800℃): 0.35 w/n.k. Strength: 4-5Mpa.

Packing form: pallet. Product category: Mullite products.

Specifications: 230*230*65mm; 250*230*97.

Rongsheng Refractory Materials Manufacturer can customize the dimensions and specifications of Hang roof brick Mullite for enterprises according to the different sizes of various types of industrial kilns. Each company can also send us drawings, and we will customize the size specifications for the company based on the company’s design drawings.

Hang Roof Brick Mullite Uses

Various industrial kilns, such as bell furnaces, heating furnaces, cracking furnaces, heat treatment furnaces, shuttle kilns, tunnel kilns, roller kilns, enamel kilns, ceramic kiln roofs and walls, and thermal insulation lining materials.

Advantages of Tunnel Kiln Lightweight Mullite Brick Hang Roof Bricks

Tunnel kiln mullite Hang Roof, which includes multiple mullite groups. Each mullite set consists of two mullite Hang Roof Bricks, mullite T-shaped pendants, and metal hooks. The mullite T-shaped pendant as shown in the figure includes a plug-in board, a connecting block is provided on the plug-in board, and a metal hook is provided on the connecting block. Moreover, the mullite Hang Roof tiles are square in shape, and one side of the mullite Hang Roof Bricks is provided with a mullite T-shaped slot. Mullite T-shaped slots provided on the two mullite Hang Roof tiles of each group of mullite groups are respectively located at both ends of the insert plate. It has the advantages of lightweight, easy installation, disassembly and replacement, having good heat resistance, and the metal hook is not easy to be corroded and damaged.

Tunnel kiln mullite Hang Roof tiles include multiple mullite groups. Each mullite group consists of two mullite Hang Roof Bricks, mullite T-shaped pendants, and metal hooks.

Tunnel kiln mullite Hang Roof bricks are made of high-quality and high-purity refractory powder, and organic composite fillers are added according to the required proportion of the product. Lightweight mullite products are formed by vacuum extrusion and high-temperature sintering.

Advantages of tunnel kiln mullite Hang Roof Bricks: low thermal conductivity and low heat capacity. High purity and low impurity content. Resistant to high temperatures and can be in direct contact with flames. High strength and excellent thermal shock resistance. Can be cut at will.

Advantages of Kyanite Lightweight Mullite Refractory Bricks

As a raw material for refractory materials, kyanite has been used in a variety of products. The ideal chemical composition of kyanite is AL2O3·SiO2, which is a homogeneous multi-phase variant with the same composition as andalusite and sillimanite. Kyanite is denser than andalusite and sillimanite. This high density is in a metastable state under normal pressure and can spontaneously decompose into a low-density mineral combination, namely mullite-quartz, at a certain temperature.

Lightweight mullite bricks are used for high-temperature kiln linings that are not in contact with the melt. Not only high operating temperature is required, but also low thermal conductivity is required. For general lightweight refractory materials, they are not only required to have a high operating temperature but also need to have a low thermal conductivity. For lightweight refractory materials, the smaller the gap size within a certain range, the lower the thermal conductivity. Therefore, the micropores formed by the decomposition and expansion of kyanite are favorable conditions for improving the thermal insulation performance of lightweight mullite bricks.

Lightweight mullite refractory bricks have the characteristics of high operating temperature, low heat capacity, low thermal conductivity, high strength, and good thermal shock resistance. The AL2O3 content of lightweight mullite bricks synthesized from kyanite and industrial alumina powder is 67.1%, which is significantly higher than that in foreign countries.

Buy high quality Hang roof brick Mullite, Hang roof brick High aluminum poly-light brick. Rongsheng refractory materials manufacturer can customize the shape, size, specifications, etc. of hanging bricks for customers. Contact us for a free quote.

Refractory Materials for Reactors Producing Sulfur from H2S

2024-07-26 by globalrefractory

In the sulfur reactor, the H2S combustion furnace has a higher operating temperature and is one of the single equipment with the highest design temperature. In its design, in order to improve the recovery rate of sulfur, the method of preheating the raw gas and air is generally used to increase the furnace temperature. At present, the operating temperature of the reactor has been increased from 1050°C to 1450°C. Coupled with the combustion support of alkane gas, the furnace temperature may reach 1600°C. Therefore, it is a great challenge to the refractory materials built in the furnace.

The production of sulfur currently uses the Claus process to recover sulfur from acid gas containing H2S. This production process is common in coal gasification or petrochemical industries, because H2S is the main by-product in the production of such industries. The process principle is to use the partial combustion method in the sulfur recovery device, that is, introduce all the acid gas into the combustion furnace, and distribute the air according to the complete combustion of hydrocarbons and the complete combustion of 1/3 H2S to generate SO2. For H2S, the reaction results in that about 65% (mass fraction) of H2S in the furnace is converted into S vapor, 1/3 of the remaining 35% (mass fraction) of H2S is burned into SO2, and 2/3 remains unchanged. Among them, 65% of the S vapor generated by the reaction is condensed and captured in the waste heat boiler, while the remaining H2S and SO2 reacted in the furnace react under the action of the catalyst in the converter to further generate S. In order to react uniformly and prevent impact on the hot end of the waste heat boiler, a flower wall is built in the middle of the furnace. The main medium in the furnace is H2S + SO2 + high-temperature gas containing S vapor. The operating pressure is not greater than 0.05MPa, and the operating temperature is not greater than 1450°C. Made of refractory materials, thickness 400mm.

Difficulties in Selecting Refractory Materials for Masonry Reactors Producing Sulfur

(1) The furnace temperature is high. The working temperature is 1100~1450℃, which is a furnace with a higher working temperature. Under occasional operating conditions, the furnace temperature may reach 1600°C or higher.
(2) There are various corrosive components such as H2O, H2S, SO3, SO2 and S vapor in the furnace. H2S has reducing properties. As a result, there are strict restrictions on certain impurity components in furnace lining materials.
(3) Acid gas combustion furnace has no heating surface inside the furnace. Any large fluctuation during combustion means a thermal shock to the furnace lining, which requires the furnace lining to have good thermal shock resistance.
(4) The combustion furnace has strict requirements on wall temperature and requires the furnace lining material to have good thermal conductivity.

Selection of Several Domestic Mainstream Refractory Materials

2.1 Corundum castable material material

At the earliest, corundum castable linings were commonly used as lining materials for acid gas reactors in sulfur recovery units at home and abroad. The reason is that the corundum castable lining not only has a higher fire resistance temperature but also has better wear resistance. However, due to its poor thermal shock resistance, problems such as peeling and falling off may occur within a short period of time, and it will be gradually eliminated over time.

2.2 High alumina brick + corundum brick material

The lining material of the original acid gas combustion furnace is high alumina brick + corundum brick. The brick joints are one of the weakest links. Damage to the brick joints often leads to overall deformation and collapse of the masonry. On the other hand, high alumina bricks and corundum bricks are difficult to process and manufacture, difficult to fit into some special-shaped parts, and the cost is also high.

2.3 Steel fiber castable material

Steel fiber castables have achieved good results in catalytic converters and other applications due to their good fire resistance. However, in the case of acid gas combustion furnace, this material is prone to problems such as agglomeration and deep cracks.

2.4 Combined material of castable and ramming material

Castable combined with ramming makes a very good high-temperature-resistant lining. The composition (mass fraction) of ramming material is 85% AL2O3+15%SiO2. Has the following salient features:

①High temperature resistance (up to 1800℃) and high strength.
②The furnace wall support is hanging type, which is not easy to deform or fall off.
③The insulation layer is constructed by pouring, and the working layer is constructed by pounding. It can be made into any shape (especially in special shapes) and is easy to construct. Its combined structure is dense and solid, with no gaps in the walls.
④When the lining is supported by anchors, the furnace wall can withstand peeling and protrusion, making maintenance easy.
⑤The lining material has good peeling resistance and will not embed foreign matter.
⑥Short oven time, fast and economical construction

To purchase high-quality refractory lining materials, please contact us. We can provide high-quality refractory products and customer service.

Furnace Lining Refractory Materials for Sulfur Making Furnaces

2024-07-19 by globalrefractory

The sulfur-making combustion furnace is one of the core equipment of the sulfur recovery unit, where 60%-70% of the hydrogen sulfide is converted into elemental sulfur. It controls the process of converting 1/3 of hydrogen sulfide into sulfur dioxide and complete combustion with ammonia and hydrocarbons. It can be said to be the heart of the combined device. Therefore, the operation of the sulfur combustion furnace directly affects the sulfur recovery rate and sulfur dioxide emissions. One of the most direct factors affecting the performance of a sulfur furnace is the refractory lining of the furnace. The originally designed refractory layer was made of large corundum mullite bricks, and the thermal insulation layer was made of lightweight insulating castables. However, in the early stages of operation, the outer walls of the sulfur furnaces experienced varying degrees of over-temperature and even red heat.

The sulfur recovery and sulfur production system adopts the partial combustion method to introduce all the raw gas into the sulfur production combustion furnace. In the sulfur-making furnace, the air distribution ratio is strictly controlled according to the amount of oxygen required for complete combustion of 1/3 of hydrogen sulfide, ammonia, and hydrocarbons. The amount of sulfur dioxide generated after hydrogen sulfide is burned satisfies H2S/SO2 to be close to 2. About 60% to 70% of hydrogen sulfide and sulfur dioxide react at high temperatures in the furnace to form gaseous sulfur. The operation of the sulfur-making combustion furnace directly determines the sulfur recovery rate of the entire sulfur-making system and whether the exhaust emissions meet the standards. The components of raw sour gas are relatively complex, including H2S, CO2, H20, NH3, H2 hydrocarbons, etc. The chemical reactions that occur in the furnace are also relatively complex.

Refractory Materials for Sulfur Making Furnaces

Conditions that Lining Refractory Materials Should Meet when Designing Sulfur Furnaces

Conditions that lining refractory materials should meet when designing sulfur furnaces. Able to withstand higher temperatures, the operating temperature of the sulfur furnace furnace is 1250~1400℃, which may reach 1600℃ under abnormal conditions. Since the supply of raw materials is unstable and most of them are corrosive, they must have strong corrosion resistance. There is no heating surface in the furnace, and the lining must have stable thermal shock resistance. It has stable thermal conductivity and the furnace wall temperature can be controlled to ≤300℃. For furnaces with excessively large diameters, the lining should have good high-temperature stability. It has a long service life and meets the requirements of full load and long-cycle operation. Has good volume stability. Masonry is convenient and the construction period is short.

Thickness of Refractory Material Lining Sulfur Furnace

The total thickness of the lining refractory material of the sulfur-making combustion furnace is designed to be 400mm. The refractory lining in the upper 1/2 part of the front cone section adopts a double-layer lining structure, 200mm alumina hollow ball castable + 200mm corundum refractory plastic. The acid gas inlet distribution ring bricks have a four-layer lining structure, namely 100mm lightweight insulating castable + 150mm corundum castable + 150 corundum mullite bricks + acid gas inlet distribution ring bricks. The rest of the structure is a double-layer lining structure, that is, 220mm corundum refractory plastic + 180mm lightweight heat-insulating castable. The anchoring system consists of anchor bricks with C-shaped hooks and V-shaped nails. The flower wall tiles, annular channel ring tiles, and acid gas inlet distribution ring tiles are all made of corundum mullite bricks. The anchor bricks are arranged on 2/3 of the furnace, and the center distance between adjacent anchor bricks is 400mm.

Construction of Lining Refractory Materials for Sulfur-Making Combustion Furnace

Construction method: The insulation layer is constructed by manual pounding. Use a forced mixer to mix the materials, and add water in strict accordance with the mix ratio. The mixing time is generally about 3 minutes, subject to uniform color. The mixed materials should be used within 10 minutes. It is strictly forbidden to add water to the hardened materials for reuse. The construction joints of the two layers of insulation should be staggered by more than 100mm. The insulation layer should be maintained in moisture, and the second layer of insulation or refractory plastic can be constructed only after at least 24 hours. When the entire ramming construction is completed, remove the formwork and trim the lining surface to the designed thickness. The expansion joint should be cut according to the drawing requirements, generally 60mm deep and 2-3mm wide. Horizontal and vertical expansion joints should be left at the junction of the furnace roof and furnace wall, and the joints should be filled with fiber cotton. After the lining has been trimmed, vent holes should be punched to allow moisture in the material to escape. Before and during the drying process, steam, water, oil and other impurities are not allowed to corrode the plastic. Corundum bricks should be cured naturally after being laid wet, and contact with water is strictly prohibited. The original expansion joint is widened to about 3mm, and then filled with zirconium-containing fiber blankets. The flower wall tiles and acid gas inlet distribution ring bricks are laid wet, with staggered joints, and the mortar fullness is greater than 90%. Refractory plastic is a pre-mixed and pre-pressed blank material. When using it, you only need to pound it tightly without stirring or adding binders. The construction is simple and the on-site operating conditions are good. At the same time, because plastic is a gas-thermohard material, no maintenance is required. The construction period is short and suitable for rapid repair operations of the lining. The lining structure has good thermal shock resistance and resistance to thermal stress. However, the continuity and consistency of construction must be ensured.

To purchase high-quality refractory lining products, please choose a competent manufacturer and seller of refractory materials. For example, Rongsheng Refractory Material Manufacturer. Rongsheng’s refractory products have been sold to more than 100 countries and regions around the world. Our refractory products have reliable product quality and our comprehensive customer service ensures the long life and efficient operation of the refractory lining. Contact us for a free quote.

Refractory Ceramic Balls High Strength – Refractory Ceramic Heat Storage Balls

2024-07-12 by globalrefractory

Refractory ceramic balls and refractory balls are made of industrial alumina and refractory kaolin as the main raw materials, through scientific formula, shaping, and high-temperature calcination. it has:

High mechanical strength and long service life.
It has good chemical stability and does not react chemically with materials.
Good high-temperature resistance, the heat resistance temperature of refractory porcelain balls can reach 1900 degrees Celsius.

It is especially suitable for high and low-temperature conversion furnaces, reforming furnaces, hydroconverters, desulfurization tanks, and methanation furnaces in fertilizer plants. It plays the role of dispersing gas and liquid, and supporting, covering and protecting the catalyst. Refractory ceramic balls can also be used in hot blast furnaces and heating conversion equipment in the steel industry.

Classification of refractory balls: Refractory porcelain balls are divided into ordinary refractory balls and high-aluminum refractory balls. Ordinary refractory balls are suitable for converters and conversion furnaces in the sulfuric acid and fertilizer industries. High-aluminum refractory balls are suitable for hot blast furnaces, heating conversion furnaces, and other equipment in urea, steel and other industries.

Refractory Ceramic Heat Storage Balls

Heat storage ball is an excellent refractory material. It has significant characteristics such as low shrinkage of the refired line, high softening temperature under high temperature load, corrosion resistance, high strength, large heat storage and release, good thermal shock stability, good thermal conductivity, and small thermal expansion coefficient. By double preheating gas (blast furnace, converter) and air (combustion air single heat storage method is used for oil, high calorific value gas, etc.), the regenerative heating furnace can reduce the smoke exhaust volume by 20-50%. The exhaust gas temperature drops to less than 150 degrees, and the output increases by 15-20%. The billet heating time is shortened by 50%, and the oxidation and burning loss is reduced by 30-50%, which is an environmentally friendly and energy-saving effect.

1) The specific surface area of heat storage balls can reach 240m2/m3.
2) Numerous small balls divide the air flow into small streams. When the air flows through the heat storage body, it forms strong turbulence, which effectively breaks through the boundary layer on the surface of the heat storage body. And because of the small ball diameter, small conduction radius, small thermal resistance, high density, and good thermal conductivity, it can meet the frequent and rapid reversal requirements of regenerative burners.
3) The regenerator can use 20 to 30 reversals per hour. After the high-temperature flue gas flows through the regenerator bed, the flue gas can be reduced to about 130°C and then emitted.
4) When high-temperature gas and air flow through the regenerator in the same path, they can be preheated to only about 100°C lower than the flue gas temperature. The temperature efficiency is as high as over 90%.
5) Because the heat storage body is very small in size and the small pebble bed has strong circulation capacity, even if the resistance increases after dust accumulation, the heat exchange index will not be affected.
6) Thermal storage balls have the characteristics of strong resistance to oxidation and slag.
7) The ceramic ball is very convenient to replace and clean, and can be reused.

What are the Functions of Refractory Balls

Refractory ball is a kind of sphere made of industrial alumina and refractory kaolin as the main raw materials, and calcined at high temperature through scientific formula. It is mainly divided into high-aluminum refractory balls, silica refractory balls, magnesium-aluminum refractory balls, porcelain balls, etc. Converters and shift furnaces for the sulfuric acid and fertilizer industries. High-aluminum refractory balls are suitable for hot blast furnaces, heating conversion furnaces and other equipment in urea, steel and other industries.

The main role of refractory balls in actual use is due to their good high-temperature resistance and high hardness. Putting the refractory balls evenly into the heating furnace can evenly distribute the gas. Evenly dispersed gas can reduce the effect on the catalyst and extend the service life of the catalyst. At the same time, it has high hardness, so it can play a supporting role in heating objects in the heating furnace.

The working principle of refractory balls is to divide the air flow into small streams by dividing many small balls. The airflow flows through the heat storage body, forming intense turbulence, which effectively breaks through the boundary layer on the surface of the heat storage body. And because the ball diameter is small, the conduction radius is small, the density is high, and the thermal conductivity is good. Therefore, the requirement of frequent and rapid reversal of the regenerative burner can be realized.

High-aluminum refractory balls are often used during use. Although high-aluminum refractory balls are very hard, they become very brittle after high temperatures. Dry grinding can easily cause cracks in the ball stones and pits on the surface of the ball stones, resulting in very high wear. Therefore, we must pick out the spheres with high cracking and wear during actual use.

Uses of Acid-Resistant Refractory Coatings

2024-07-05 by globalrefractory

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.

Chemical Reactions between Refractory Materials and Various Gases

2024-07-052024-06-21 by globalrefractory

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.

Refractory Materials for the Settling Chamber of Zinc Volatilization Rotary Kiln

2024-07-042024-06-07 by globalrefractory

· [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.

Effects of 5 Different Types of Additives on the Performance of Cement Kiln Entrance Castables

2024-07-042024-05-24 by globalrefractory

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).