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refractories for cement rotary kiln

everything you need to know on rotary kiln refractory

everything you need to know on rotary kiln refractory

Refractory, or the lining utilized on the interior of rotary kilns, is a critical component in ensuring process efficiency and prolonging the life of a rotary kiln. Here, well discuss everything you need to know about refractory, including how it works, the different types, and best practices for preventative care.

Rotary kilns employ high temperatures to cause a chemical reaction or physical change in a material. In most cases, these high operating temperatures would immediately destroy an unprotected carbon steel shell. For this reason, refractory is used.

Only direct-fired rotary kilns employ refractory; in an indirect-kiln, heat transfer occurs primarily through the kiln shell wall. Refractory would be another barrier for heat to pass through before it is in contact with material, reducing the efficiency of the process. Because of this, instead of using refractory, indirect-fired kilns typically rely on a more heat resistant shell.

Further necessitating the need for refractory, direct-fired kilns typically do not utilize combustion chambers, so the flame is in constant direct contact with the internals. Flame temperature can typically range anywhere between 1600 3200 (depending on excess air) a harsh processing environment that carbon steel is not capable of withstanding.

As the skeleton of the system, protecting the shell is paramount to prolonging the life of the equipment; a major repair or total replacement of the shell is a substantial undertaking, requiring significant downtime and repair costs. For this reason, choosing the right refractory configuration and taking measures to protect that refractory once operational is critical.

While the main objective of refractory is to protect the kiln shell, refractory also serves to minimize heat loss. A kiln with sub-par refractory may protect the kiln shell, but allow significant heat loss, reducing overall process efficiency and increasing operational costs.

Castable refractory comes in a powder form and is mixed with water on-site. Before the mixture can be put in place, anchors are installed. These y-shaped anchors are similar to rebar in cement; they help give the castable lining its strength. Once these anchors are in place, the cement-like mixture is pumped into the lining of the rotary kiln, and allowed to cure for several days.

Castable refractory has a similar material cost to brick. However, brick installation is much more labor intensive, as each brick is individually installed. This makes the overall cost of a brick lining more expensive than castable.

Besides lower overall cost, the advantage to using castable refractory in a rotary kiln is that it is usually easily patched when a problem is encountered. Down time is typically minimal, because the problem area can be cut out and new refractory poured into the cavity.

The disadvantage to using castable refractory in a rotary kiln is that it is very susceptible to installation problems. When castable refractory is expertly installed, it can nearly match the quality of brick. But if installed incorrectly, there can be a considerable difference in quality, and the life of the refractory can be severely compromised.

Although slightly more expensive than castable, brick does not require anchors, and its quality is superior, but as mentioned, incurs greater install costs. When processing a highly abrasive material, brick refractory is advisable most of the time, as castable does not have the durability to stand up against abrasive materials as well as brick.

The disadvantage to brick refractory is that it is kept in place much like a roman arch: bricks are held in place by the pressure of the other bricks pushing against each other. When a problem is encountered, typically the failed brick needs to be replaced, but when one brick is relying on the bricks around it to hold it in place, often one cannot replace just one brick, and whole sections of the refractory must be replaced. Unlike castable refractory, the repair of a fail in brick refractory is much more involved.

There is more to refractory than just the choice of material; refractory is a customizable part of rotary kiln design and can be tailored with multiple layers to meet the demands of a given application.

When efficiency is of great concern, or when extreme temperatures are involved, it is common to employ both a working layer, and an insulating layer. Layer thickness can also vary, with total refractory thickness generally falling between 4.5 12, pending process temperatures..

The working layer is the layer of refractory that is in direct contact with the material being processed. This layer is a dense, durable lining designed to withstand the high temperatures within the rotary kiln, as well as the constant abrasion from the material.

When it comes to refractory, the more dense it is, the less insulating capabilities it has. This means that even though there may be a working layer in place, the heat can easily pass through it to the shell of the rotary kiln. For this reason, an insulating layer is needed beneath the working layer. The insulating layer serves as insulation to protect the shell of the rotary kiln so the high temperatures within cannot reach the shell and damage it.

Typically the working layer and the insulating layer are made of the same material (ie. brick or castable), with varying chemistries. The working layer tends to be a higher density, strongermaterial that is more conductive. The insulating layer does not need these qualities, and tends to be softer, lighter, and less conductive, therefore more insulating. These two layers often vary in thicknesses, determined by the needs of the rotary kiln and what material is being processed. In some cases, such as when temperatures are fairly low, or when efficiency is not a concern, a single working layer may be all that is needed.

In contrast, when insulation is extremely critical, an optional third layer of ceramic fiber backing may be used. This thin, but very efficient layer is similar to fiberglass insulation found in a house, but it is much more compressed. The decision to employ this layer comes with some responsibility. Should a crack in the refractory occur and go unnoticed, it is possible for the high heat inside the rotary kiln to reach this backing and burn it up. This would create a gap between the refractory and the shell of the rotary kiln, which would cause disastrous problems. Due to this potential of increased risk, this third layer is not always appropriate.

The processing environment within a direct-fired rotary kiln can be harsh. The combination of constant rotation, extreme temperatures, heavy loads, and abrasive and corrosive environments, has the potential to cause significant damage or catastrophic failure to a kilns shell. Once your rotary kiln refractory is installed and in use, it is important to take the extra steps to ensure it is properly maintained.

A well-installed, high quality refractory can have a lifespan of many years, but there are factors that can cut refractory life short. While early signs of refractory failure can be hard to spot, the good news is, many of the things that can cause refractory failure are preventable. The two primary causes of refractory failure are cycling and chemical incompatibility.

The biggest source of refractory failure is what is called cycling. Cycling is simply the heating up and cooling down of the rotary kiln. Each time the rotary kiln is heated, the refractory expands with the drum, and as the kiln is cooled, the refractory retracts. If a kiln is constantly being turned on and shut down, the refractory can easily become stressed, resulting in cracks.

Similarly, cracks can also occur from heating or cooling the kiln too quickly. To maximize refractory life, it is important to try to reduce cycling as much as possible, keeping shut downs to a minimum.

Chlorides can aggressively attack refractory, causing excessive wear because of their corrosive nature. When these chemicals are identified up front, refractory can be designed with this in mind to help reduce the potential for excessive wear. Similarly, unknown components in a material or a change in feedstock can also result in excessive wear on refractory.

Operators should be well-versed in the proper operation of the kiln and what to look for to spot potential problems. Operators and maintenance personnel should always follow the guidelines for safety and maintenance set forth by the original equipment manufacturer.

Regularly observing the kiln to check for any visual, auditory, or other abnormalities can mean the difference between a small repair and a catastrophic failure. As part of routine observations on the unit, the kiln shell should be regularly measured with a temperature gun to check for hot spots.

This can be done by picking a spot on the rotary kiln shell, and holding a temperature gun in place. As the rotary kiln rotates, that spot should read the same temperature for the entire circumference of the shell. For example, a temperature reading of 400, 400, 700, 400 would likely indicate a failure in refractory. Left untreated, this could lead to severe damage to the rotary kiln shell.

In addition to circumference temperature being the same in a given location, there should be a gradual shift in temperatures from one end of the kiln to the other, not a drastic change. Catching these problems early is important to minimizing the potential for damage.

Additionally, having a service technician visit the site to observe and inspect the kiln every so often is also considered best practice in preventative maintenance. Depending on what the original equipment manufacturer recommends, this is generally on an annual basis, but may be more frequent for especially demanding settings.

Refractory failure can have disastrous results. Even a small crack can allow heat to reach the rotary kiln shell. It is important to routinely temp gun the exterior of the rotary kiln shell, ensuring that the temperature is consistent for the entire circumference of the drum.

Refractory is a critical component in the design of a direct-fired rotary kiln, helping to protect the kiln shell from the harsh processing environment within. A customizable part of kiln design, refractory can be engineered to suit the unique needs of an application, with factors such as material and multiple layers coming into play.

As the only barrier between the shell and the kiln interior, protecting and maintaining refractory is of the utmost importance in order to prolong the life of the equipment and avoid potential catastrophic failures.

cement kiln refractories

cement kiln refractories

Refractories play a critical, if unseen, role in both the rotary kiln lining, and the lining of the high volume static equipment areas that comprise a modern pre-calciner kiln system.The durability of the rotary kiln brick lining generally determines the duration of a kiln operating campaign. Whilst great efforts are made to ensure appropriate refractory brick materials selection, installation, deployment (zoning) and the optimisation of the kiln light-up, it is primarily the nature and stability of the subsequent kiln operation that influences rotary kiln lining life.

A large number of kilns now use alternative fuels. Many of them substitute these alternative fuels through the main kiln burner as well as in the pre-heater / pre-calciner; the chemical and heat-release changes caused by inevitable short-term fluctuations in the fuel(s) mix has a major influence on the thermal, coating and atmosphere conditions existing through the rotary kiln into the pre-calciner.Expert systems are available that help limit the influence of fuel mix fluctuations on the flame shape, but not many cement kilns are equipped with such systems. Consequently, the main influence of the use of alternative fuels is often on clinker chemistry due to the different ash compositions of individual alternative fuels.Such fuel variations may produce any or all of the following:

Much can be learned from the clinker chemistry and microscopy about the environment existing within the kiln system. The clinker mineralogy, microstructure, minor phases, macrostructure and variability can each help to define more precisely the atmosphere and process conditions existing in the rotary kiln and clinker cooler. If any of the clinker parameters are found to be outside a safe range, or potentially indicative of conditions damaging to the coating or to the kiln refractory, kiln operators can use this information to attempt to achieve safer and more stable kiln conditions, thus reducing thermal and chemical stresses on the kiln lining.

Articles like this one can provide a lot of useful material. However, reading an article or two is perhaps not the best way to get a clear picture of a complex process like cement production. To get a more complete and integrated understanding of how cement is made, do have a look at the Understanding Cement book or ebook. This easy-to-read and concise book also contains much more detail on concrete chemistry and deleterious processes in concrete compared with the website.

Almost everyone interested in cement is also concerned to at least some degree with concrete strength. This ebook describes ten cement-related characteristics of concrete that can potentially cause strengths to be lower than expected. Get the ebook FREE when you sign up to CEMBYTES, our Understanding Cement Newsletter - just click on the ebook image above.

cement kiln refractories course

cement kiln refractories course

Principal refractory performance issues in the rotary kiln, refractory materials, process efficiency of linings, inspection, repair and maintenance, optimised refractory usage. A total course for cement production staff who, until now, have only been able to 'learn on the job'.

The Cement Kiln Refractories e-Learning course is intended to fill a gap in the cement industry where no formal training in refractories is generally available. Engineers will no longer be obliged to gain their refractories experience 'on the job', with the inevitable consequence of perpetuating mistakes.This certified training will provide the accumulated experience of more than 30 years in cement kiln refractory engineering, and will allow informed decisions to be made regarding selection, installation and maintenance of refractories and refractory systems.The course begins with the key principals of refractory materials for cement kilns, covering selection, installation and maintenance for all sections of the kiln.Inspection, condition monitoring, preventative and planned maintenance are all covered and also cement kiln refractory performance benchmarking and the development of refractory improvement plans. Important relationships between the refractory lining and process efficiency will be discussed in some detail.On completion of this course, delegates should have a firm appreciation of the importance of the many refractory choices to be made in both the rotary kiln and static plant areas such as preheaters, precalciners, kiln hoods and coolers.Successful participants will qualify for certification from the Independent Cement Producers Association and will be much better placed to contribute to improvement plans within their factories and production lines.

refractory solutions for the cement industry | calderys

refractory solutions for the cement industry | calderys

Calderys has been providing refractory solutions for the cement industry for decades and is a reference supplier worldwide. Our team of experts selects the best suited products and services for your process requirements.

You hereby acknowledge that the information and documentation obtained and/or downloaded from this Website should be used as indication only, at your own risk and discretion, and that such information should be checked for accuracy and confirmed with a Calderys sales manager, along with the products availability.

Indeed, the information contained in the Website does not constitute an offer to sell any product nor a warranty on the products' quality or characteristics. The information disclosed on the Website is provided on an as-is basis and Calderys hereby disclaims all warranties and representations of any kind, express or implied, including but not limited to the accuracy, completeness, merchantability, fitness for a particular purpose and non-infringement of any information disclosed herein, and that access to the Website will be continuous or uninterrupted.

All documents and information contained in the Website are Calderys exclusive property. Calderys reserves its right to revise, at any time, without notice, the information on the Website and makes no commitment to update such information on a regular basis.

refractory material for cement rotary kiln | agico cement manufacturing

refractory material for cement rotary kiln | agico cement manufacturing

According to statistics, the refractory material consumed by the cement industry accounts for about 10% of its total production. With the further development of the cement industry, the demand for refractories has not only increased in quantity, but also in quality. In the cement plant, the development of refractories for rotary kilns has gone through a long process, which makes its service performance keep improving and the service life of kiln lining keep extending, but at the same time, there are still some problems. Moreover, with our increasing awareness of environmental protection, the high-quality spinel refractories, magnesia refractories, calcium refractories and zirconium refractories have become the development direction.

The sintering zone has the worst working environment in the whole cement rotary kiln system. It bears more abrasion than the preheating zone and cooling zone. Its service life mainly depends on the durability of the lining refractory materials at the sintering zone. Due to the influence of the thermal-mechanical and thermo-chemical comprehensive effects, the refractories in this area should have good physical and chemical indexes.

When the kiln turns one circle, the refractory material in the rotary kiln will be exposed once in the gas. In the rest of the time, it is covered by the cement raw materials. Because the gas temperature in the kiln is higher than that of the raw material, the refractory temperature will be subject to periodic thermal shock, and the temperature difference can reach over 400, which requires the refractory material to have excellent thermal shock resistance.

The cement clinker has strong alkalinity, and its silicate liquid formed at a high temperature can easily infiltrate into refractory bricks, resulting in changes or even damage in chemical composition and mineral composition of refractory materials. At the same time, the gases produced by fuel combustion and the volatilized sulfur, chlorine and alkali also have a strong chemical erosion effect on refractory materials. Therefore, the refractory material used in the sintering zone of cement rotary kiln should have excellent corrosion resistance.

When the cement rotary kiln is in normal operation, the hot surface of lining brick in sintering zone needs stable kiln skin to play a protective role, reducing the melting loss caused by high-temperature cement raw materials. At the same time, there are some certain requirements for the thickness of kiln skin, because when the kiln skin is thin, the melting loss of the refractory material is large, but if the kiln skin is too thick, it will not only affect the normal calcination and reduce the output, but also fall off some refractory materials due to the collapse of the thick kiln skin so that reduce the service life of the whole kiln lining.

The refractory materials used in the sintering zone of cement rotary kiln should not only have the properties we mentioned above but also have the properties of low thermal expansion coefficient, good flexibility, etc., so as to achieve good service effect. Therefore, understanding the characteristics of various refractories and choosing refractories reasonably are the main ways to improve the service condition of kiln lining and reduce the consumption of refractory materials.

The magnesite-chrome brick has excellent corrosion resistance and spalling resistance. At the same time, it has high strength, so it is widely used in the sintering zone of cement rotary kiln. However, the residual bricks after the magnesite-chrome brick are used contain a large amount of Cr6+, which will cause long-term environmental pollution. And there are fewer and fewer high-grade chromium ores in the world. This requires us to develop other refractories that can replace magnesite-chrome. In addition, magnesite-chrome bricks have strong volatility at high temperature, which will reduce the high temperature stability, slag resistance and spalling resistance of refractories, and shorten the service life of magnesite-chrome bricks. Although the chromium-free cement rotary kiln has been required for many years, it is still impossible to completely replace magnesite-chrome bricks with chromium-free bricks.

Japan is the first country to use magnesite-spinel bricks in cement rotary kilns. The purpose is to solve the Cr6+ pollution caused by magnesite-chrome bricks in use. Compared with magnesite-chrome bricks, magnesite-spinel bricks can improve the creep resistance and thermal shock stability of rotary kiln lining, and maintain good stability in oxidation or reduction atmosphere. Although the use of magnesite-spinel brick solves the chromium-free problem of cement rotary kiln to some extent, there are still many problems. For example, it is difficult to form a stable kiln skin by using magnesite-spinel brick in the rotary kiln sintering zone, which is easily affected by the atmosphere and heat load, so its service life has always been the bottleneck of the cement kiln. Secondly, it has high thermal conductivity, wastes resources and is easy to peel off. Therefore, improving the stability and spalling resistance of magnesite-spinel brick kiln skin is one of the important measures to improve the service life of kiln lining.

Dolomite bricks are regarded as the substitute of magnesite-chrome bricks which are widely used in cement rotary kilns. The biggest characteristic of it is the price advantage and the stable kiln skin formed by it. However, this kind of brick has poor hydration resistance. It is easy to react with water vapor in the air during production, transportation and kiln shutdown, which is the main factor preventing the large-scale use of dolomite refractories. In addition, the thermal shock stability of dolomite refractories is poor. When the cement rotary kiln is operated intermittently, it is easy to produce a large number of cracks. The effective ways to improve the thermal shock stability of dolomite refractories are to adopt appropriate particle composition, improve the rotary kiln system and add appropriate ZrO2.

AGICO Group is an integrative enterprise group. It is a Chinese company that specialized in manufacturing and exporting cement plants and cement equipment, providing the turnkey project from project design, equipment installation and equipment commissioning to equipment maintenance.

cement industry refractories - rs kiln refractory bricks

cement industry refractories - rs kiln refractory bricks

Get Free Quote Your Name (required) Your Email (required) Your Phone Required Products (required) Enquiry Information Related PostsRefractory Bricks Used in Ceramic CupRefractory Bricks Used in Ceramic CupAlumina Silica Brick for SaleMicro-expansion High Alumina BrickElectric Arc Furnace Refractory MaterialBasic Fire BricksHigh Alumina Bricks SupplierSteel Ladle Al2O3-MgO-C Refractory aluminabricks 0 Comments

Rongsheng Refractory Supplier provides kinds of refractory bricks and monolithic refractories. Exclusive customer service and refractory lining material solutions for metallurgy, nonferrous metals, building materials, electric power, petrochemical and other industries. Save production costs and improve economic efficiency.

refractory material for cement rotary kiln hoods |rs refractory castable

refractory material for cement rotary kiln hoods |rs refractory castable

For some large rotary kilns, the heat load on the lower part of the Kiln Hoods is relatively high. If the general high alumina castable refractory is not well maintained and temperature rise controlled, they are prone to bursting and falling off. The top of the Kiln Hoods is close to the tertiary air duct, and the dust-laden airflow is relatively serious. Moreover, the construction of the top castable is relatively difficult, and the fluidity and early strength of the material are relatively high. Rongsheng refractory castable cement manufacturer recommends that the Refractory Material for Cement Rotary Kiln Hoods adopts high-strength wear-resistant castables with good high-temperature performance, strong thermal shock resistance, and wear resistance.

The Kiln Hoods is the kiln head part of the rotary kiln, and the cooler is supporting equipment for the rotary kiln. The top of the cooler has a high working temperature and large temperature changes. The low walls on both sides of the front end are long-term abraded by the high-temperature clinker coming down through the kiln mouth and also endured by certain mechanical and thermal stresses. The operating environment of these two parts is similar. Therefore, refractory manufacturers generally recommend the use of refractory materials of the same material. Rongsheng refractory manufacturers generally recommend the use of refractory castables in these two parts.

According to the operating characteristics of the above parts of the cement rotary kiln, it is recommended to use high-strength wear-resistant castables with good high-temperature performance, strong thermal shock resistance, and wear resistance.

Rongsheng refractory material manufacturer provides special kiln hoods refractory castable products for cement kilns. Moreover, Rongsheng manufacturers can adjust the refractory formula of the kiln hoods according to the specific production needs of customers. Let every customer be able to do it in the production process, minimizing costs, and maximizing benefits.

Rongsheng is an advanced refractory castable manufacturer with a fully automatic and environmentally friendly refractory castable production line with an annual output of 80,000 tons. Has served customers in more than 60 countries and regions, for example, India, Pakistan, Kuwait, South Africa, Malaysia, Vietnam, Netherlands, Philippines, Singapore, Egypt, Russia, etc. Rongsheng has customized kiln hoods refractory castables, burner refractory castables, high-alumina high-strength refractory castables, and high-strength wear-resistant castables for cement rotary kilns. The product quality and customer service of Rongshengs unshaped refractories are leading in the industry. Get more product quotations on refractory material for cement rotary kiln hoods. Please leave your contact information and specific requirements on our website page. We will provide you with refractory materials that best suit your production needs according to your actual working conditions. Save production costs and improve economic efficiency.

RS Companyis a large refractory castable cement manufacturer& factory in China. Rongsheng manufactures all kind of refractory castables, refractory cement, refractory concrete for kiln, blast furnace, and alsorefractory mortar, refractory aggregates, etc.

With the development of the past two decades, it has developed into a comprehensive enterprise in refractory material covering metallurgy, construction materials, electricity and chemical industry etc.

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