Applications of Ceramic Fiber Products

Ceramic fiber is a kind of light weight fibrous refractory. It has light weight, good high temperature performance, good thermal stability, low thermal conductivity and small specific heat. Compared to traditional insulation bricks and refractory castables, ceramic fiber products can save 10-30% energy.
Ceramic fiber first appeared in 1941 in US. Babu Wilcox Company produced ceramic fibers with natural kaolin by the blown process after melt in the electric furnace. In 1990s, with the popularization and application of zirconium-containing fiber and polycrystalline alumina fiber, the service temperature is improved to 1000℃-1400℃. However, due to the quality defects and behindhand application technology, its application is limited. Polycrystalline alumina fibers cannot be made into blanket. The specifications are monotonous, mainly cotton and block. Although the service temperature increases, the poor strength limits its application and service life.
Due to the high production cost, currently ceramic fiber is mainly used as the lining and insulation materials in various industrial furnaces fueled with coal, oil, gas and electricity and high temperature resistant reinforcing material and filter material. As a lining material, it can be used in nuclear reactors, industrial furnaces, metallurgical furnaces, petrochemical reactors, metal heat-treatment furnaces and ceramic kilns. Current insulation lining structures include refractory fiber veneer lining, refractory fiber board / refractory fiber blanket fiber lining, refractory fiber castable lining, prefabricated modular fiber lining and refractory fiber spraying lining. As a insulation material, it can be used for the fill insulation for industrial furnaces and the gaps between refractory bricks and insulation bricks, the insulation for the aircraft jet catheter, jet engines and other high-temperature pipes and slow cooling during the pipe manufacturing process. In addition, it can be used for the insulation of long-distance gas pipelines.
Zirconium-containing fiber is a kind of low-cost versatile silicate fiber made by the melting method. It can be widely used in the hot face lining of various furnaces. In practical applications, ceramic fiber cotton can be directly used as the filling materials, insulation materials and sealing materials of industrial furnaces and used to produce refractory coatings and castables.
Ceramic fiber blanket is a type of semi-rigid plate-like refractory fiber product. It has good flexibility and flexibility and can meet the needs of the construction and long-term use. It is mainly used in the lining of furnaces. Wet ceramic fiber blanket, due to its soft formability, is used in various complex parts. After dried, it becomes light, surface hardening and flexible and has better resistance to wind erosion than ceramic fiber blanket. Ceramic fiber needled blanket, is widely used for the insulation of industrial furnaces and high temperature pipes, due to good mechanical performance and no binders.
Ceramic fiber board is a type of rigid refractory fiber product. Since it contains organic binders, it has excellent mechanical properties and good resistance to wind erosion. It is generally used in the hot face of industrial furnaces and pipes.
Ceramic fiber prefabricated components are mainly used for the masonry of linings. It is convenient and fast to install. Among the ceramic fiber shaped products, the most widely used one is the ceramic fiber pipe shell. It can be used in the construction of small electric furnaces and the bushing of casting risers.
Ceramic fiber paper is usually used in the expansion joints, the nodes of the combustion furnace and plumbing equipment. Ceramic fiber rope is mainly used as non-load-bearing insulation materials and sealing materials.
In addition to insulation materials, ceramic fibers can also be used as reinforced materials and catalyst cutting body for advanced ceramics, metals and plastics.

The Selection Of Refractories For Regenerator Checkers In Soda Lime Glass Furnaces

When selecting refractories for regenerator chambers serving natural gas fired furnaces producing soda lime glass, both the functions of the refractories and the operating conditions within the checkers should be taken into consideration.
As heat exchangers, checkers should have high thermal capacity and thermal conductivity. Basic refractories and fused cast refractories are the best solution.
However, refractory selection also depends on the operating conditions, while the operating conditions depend on the position. According to the temperature, checkers can be divided into four zones: Top zone (from the first row to 1,350℃), Mid zone (from 1,350℃ to 1,000℃), Condensation zone (from 1,000℃ to 700℃) and Lower zone (from 700℃ to rider arches).

Top Zone

High temperature and batches and dusts result in chemical attack and gradual corrosion of the basic refractory bricks. If refractories are magnesia bricks, the chemical attack is up to the CaO/SiO2 ratio in the waste gases. if the radio is low, forsterite (Mg2SiO4) will be formed, which results in fissures opening within the bricks. Subsequently, silica penetrates these fissures resulting in the familiar cubic breakdown of the upper checkers. If the CaO/SiO2 ratio in the waste gases is high, a liquid phase enters into the refractory causing deformation. The best solution is magnesia bricks with high Mg content, well developed MgO crystals and a direct bonded structure. Additionally, the refractories should have low iron to avoid FeO oxidation to Fe2O3 and vice versa (Fe2O3 reduction to FeO) with volume variations and resultant brick failure.
Fused cast refractories have no surface porosity thus they are resistant to the corrosive effects of waste gases and carryover and can be used in all the checker zones. Compared to sintered refractories they are more resistant to abrasion due to their dense and homogeneous structure thus they are suitable for the top zone where there is a strong carry-over. Fused cast alumina brick is recommended for its very limited glassy phase. No glassy phase means no exudation therefore no excessive bonding with carry-over thus minimizing the risk of blockages.

Mid Zone

This zone is protected by the top checker area and temperature level is lower, thus 96% MgO with low iron and fused cast AZS 33# are recommended.

Condensation Zone

This is another critical area. The waste gases contain alkaline sulphate and SO3 which will condense out in the 1,000-700℃ range. In presence of sodium sulphate, the predominance of Na2O or SO3 in the waste gases causes chemical attack. Periclase base refractories are not chemically attacked by sodium sulphate or sodium oxide but they strongly react with SO3 forming MgSO4 causing densification of the Structure.
The chemical attack, enhanced by the presence of vanadium pentoxide when using fuel oil, breaks up the refractory and the structure densification lowers thermal shock resistance. Viable substitutes for chrome bearing refractories, which have a high resistance to condensates but cannot be used for environmental reasons, are both the spinel (MgO·Al2O3) and refractories made by periclase (MgO) and zirconia (ZrO2) having good resistance against Na2O and SO3.
When firing with natural gas, since the SO3 quantity is low, basic refractories can be used. When fused cast material is used, fused cast AZS is recommended.

Low Zone

Super duty fire clay brick can be used in non severe working conditions. 90-92% magnesia brick is recommended when firing by natural gas. Fused cast AZS 33# is also used in this zone.

Crystalline Phases And Transformation Of Silica Bricks

Silica bricks with identical chemical composition can have differing mineralogical compositions which can cause quite different behavior during use. Therefore, it is not always sufficient to evaluate silica bricks only by their chemical composition. It is essential to also consider the degree of transformation and the thermal expansion behavior of the bricks.
Silica brick contains cristobalite, tridymite and some residual quartz. The crystal phases each have a high and low temperature forms which can transform reversibly. The crystal structure of the individual SiO2 crystal phase can differ widely. This is of great importance during heating and cooling because of the change in the volume.
Quartz requires the smallest volume and the quartz glass the largest. During firing above approximately 900℃, quartz transforms into the other modifications and melt completely at 1725℃. It shows such a transformation at 573℃, tridymite at 117℃, and cristobalite between 225℃ and 270℃. The thermal expansion of cristobalite is considerably greater than that of the tridymite.
Because well transformed silica bricks contain little or no residual quartz, their behavior under the influence of temperature is largely determined by the ratio of cristobalite to tridymite. During heating up, silica bricks expand rapidly with the total reversible expansion being completed at around 800℃. Therefore they are insensitive to the temperature fluctuations above 800℃, but very susceptible below this temperature because of the sudden volume expansion. For this reason, sufficient time must be allowed for heating furnaces up to about 800℃.
During slow cooling , reversible volume decreases take place which are a result of the spontaneous transformation of the crystal structure from the high to the low temperature modification. The reversible and irreversible volume effects can cause considerable stress within the refractory brick structure.
During the firing process, the lime reacts with the quartzite components to form wollastonite. The matrix also contains very small quantities of calcium ferrite, hematite, magnetite, calcium olivine and hedenbergite, which are formed from impurities. These crystalline phases are the reason for the discoloration and spot formation on the silica bricks.
The degree of transformation of the bricks can be determined easily and accurately by the density of the residual quartz content. The density of a silica brick is lowest when the degree of transformation is farthest advanced.
The appearance of the bricks also indicates to the degree of transformation. The reversible thermal expansion also depends on the mineral composition. Tridymite and cristobalite do not expand linearly during heating but exhibit sudden changes in length both during heating and during cooling.

What is Light Weight High Alumina Brick

Light weight high alumina brick is an ideal insulating refractory, with advantages of high strength, low thermal conductivity, good insulation property and low price. For various industrial kilns & furnaces, it is a kind of essential refractory for energy saving and temperature preservation.
Light weight high alumina brick is also called high alumina insulating brick. It contains more than 48% Ai2O3 and mainly consists of mullite and glass phase or corundum. It is usually made of high bauxite and a small amount of clay. After the raw materials are grounded, it is made into mud. Then it is cast and molded and fired at 1300～1500℃. Sometimes industrial alumimum is used to replace bauxite. Inorganic matter is added as ignition loss substance in order to increase the porosity of the refractory.
It has such advantages as high porosity, good insulation effect, high mechanical intensity, small thermal conductivity and long service life. It has high cold crushing strengh,size precision and holds the most stable and lowest thermal conductivity of all insulating refractory bricks at present. Its maximum service temperature is 1350℃. Thermal efficiency and working condition can be improved, energy consumption can be lowered, productivity and significant economic results can be achieved.
It is characterized by low bulk density. The total weight of the furnace body and walls thickness can be reduced effectively.
It has found a wide application in ceramics tunnel kiln, roller kiln, shuttle kiln, coking furnaces of iron and steel industry and other thermal equipment. It is mainly used in lining and insulating layer of areas without strong erosion by high temperature melts. When in direct contact with flame, the surface contact temperature can not be higher than 1350℃.
Zhengzhou Sunrise is a refractory material supplier from China, offering high quality insulation bricks, including High Alumina Insulating Brick, Fire Clay Insulation Brick, Mullite Insulation Brick, Magnesium Silicate Insulation Board, etc..

Features of Ceramic fiber blanket

Ceramic fiber blanket, also called aluminum silicate fiber blanket, is a type of insulation refractory material, featuring high strength, light weight, non asbestos and organic binder, good high temperature stability and good insulation performance. It can effectively reduce the weight of high temperature equipment and heating time and save energy.
Ceramic fiber blanket is made of aluminum silicate with addition of auxiliary materials by the blowing technology. According to the production process, ceramic fiber blankets can be divided into two types: spun needle blanket and blown needle blanket. Especially the quality of products made by the double-side needle process is much better than common ceramic fiber blanket.
Ceramic fiber blanket has low thermal conductivity, good insulation and low thermal capacity, thus it can effectively improve the utilization of energy. It has light weight, good thermal shock resistance and good extension.
Ceramic fiber blanket has uniform diameter, long fiber and low shot content, which greatly improves its properties and performance. It contains no binder agent and has good reliability and stability in different environments.
Ceramic fiber blanket is white and has regular size. It is easy to be cut and install. It can maintain good tensile strength, toughness and fiber structure in neutral and oxidizing atmosphere. Its thermal and physical properties are bot affected by oil and can be restored after drying.
Due to its advantages, it is widely used in many fields such as lining for high-temperature reaction equipment and heating equipment in chemical industry, lining for industrial furnaces, high temperature filter material and fire protection and thermal insulation materials of high buildings.
Zhengzhou Sunrise Refractory supplies various ceramic fiber products including ceramic fiber blanket, ceramic fiber board, ceramic fiber module, ceramic fiber vacuum formed shapes, calcium silicate board, ceramic millboard, ceramic fiber paper, ceramic fiber bulk, and ceramic fiber cloth tape, rope and yarn.

Crystalline Transformation Of Silica Brick

Silica brick is one of the most widely used high temperature refractory materials. Silica brick is a light yellow refractory product made from silica rock that contain at least 90 percent SiO2. It is used primarily in coke ovens and glass furnaces. It is also used in other applications, such as glass tank walls, acid practice electric furnaces, tunnel kilns, and regenerators.
Silica is the main component of silica brick. It occurs in a variety of crystalline modifications, e.g. quartz, tridymite, and cristobalite and also as an under-cooled melt called quartz glass. The crystalline modifications each have a high and low temperature forms which can transform reversibly. The crystal structure of the individual SiO2 modifications can differ widely, so that distinct density changes occur during transformation. This is of great importance during heating and cooling because of the change in the volume.
Quartz requires the smallest volume and the quartz glass the largest. During firing above approximately 900 ℃, quartz transforms into the other modifications and melt completely at 1725℃. During slow cooling , reversible volume decreases take place which are a result of the spontaneous transformation of the crystal structure from the high to the low temperature modification. The reversible and irreversible volume effects can cause considerable stress within the refractory brick structure.
Any common silica brick having large non-transformed silica content is undesirable because it exhibits extraordinary expansion so as to impair stability of industrial furnace which employs such brick as the refractory. Therefore, the extent of transformation of silica is one of very important factors which have to be considered in designing an industrial furnace in regard to selection of material and evaluation of adequateness of the use of the selected material.
Silica brick provides a high temperature resistant and non-reactive lining. It is characterized with its good resistance to spalling at high temperatures. It also retains their rigidity, are lightweight, have a good resistance to most fluxes present in coke ovens, and offer high resistance to abrasion. It has a relatively long lifespan. It is also nonreactive with the melted glass whereas other refractories, such as magnesia brick, could discolor the final product.
Silica brick is used as a refractory in building and repairing industrial furnaces, such as coke ovens, hot blast stoves and glass furnaces. Silica brick crowns have been successfully used in glass furnaces for producing container, float glass, table-ware and TV panel glass. They have the attributes of a relatively long life, excellent insulation at a low cost, and limited defects as silica is the dominant oxide.