Frequently Asked Questions

Refractory materials should be disposed of when they complete their lifetime or subjected to the recycling process to be reassessed. In the last 20 years, refractory industry favored the recycling process and minimized the damage to the environment, as well as reduced the implementation costs. Research show that there is no difference between the thermal stability of the converted refractory materials and the newly produced ones. Thanks to the latest techniques developed in terms of recycling methods, this process is easier and efficient than ever before.

The recycling process of refractory materials varies according to the nature and structure of the material. For example, when a furnace gets disassembled, there will be many and different parts to be subjected to the recycling process. It is not possible to apply the same treatment for all of these parts. Therefore, the first thing to be done is to make a discrimination based on the category of refractory materials. MgO refractories, carbon refractories, and carbonless refractory materials is an example of this distinction. Iron and slag can be found with different rates in each of these components. Therefore, the first thing to do is to separate iron, slag and other materials from one another. This process is usually accomplished by magnetic methods, but it is also possible to do manually.

After this process, the refractory material is pulverized. For this operation (depending on the type of material) pressure, heating or milling methods can be used. The goal is to try to return the refractory material of the first and pure form. For this reason, throughout this process, all necessary measures must be taken to avoid exposure to moisture and dust. Recycling is a process which is important in many respects, as mentioned above. Monthly production of refractory waste in a steel factory is around 4,100 tons. With an efficient recycling process, a portion of refractory close to 40% can be saved and re-used in the industry. Thus, the damage to the environment will be prevented and operating costs will also be reduced significantly.

Refractory bricks are shaped refractory materials that are used in industrial furnaces. The term originates from the refractory material having a specific geometric shape, it resembles a brick in general. Since almost all industrial furnaces reach high temperatures, the refractory brick must be able to stand against the corrosive effect of the heat. That is why they are also called fire bricks. Fire bricks are produced by special methods that allow manufacture of any desired geometric shape. The important thing here is the bonding between the brick and the mortar, which determines the type of the end result. Production methods and the type of mortar used also to determine the area of application of fire bricks. If we make a classification based on this information;

Fire brick types and uses

COMPOSITE REFRACTORY BRICKS : These consist of Al2O3 - SiC, Al2O3, MgO, and ZrO2. They can withstand very high temperatures. Therefore, they are often used in the steel industry and electric arc furnaces.

THREE OXIDE REFRACTORY BRICKS : They are made of a mixture of AZS (ZrO2-Al2O3-SiO2) and CAS (CaO-SiO2-Al2O3). Since because they can withstand the effects of the corrosive liquids, they are mostly used in glass melting furnaces.

SILICA REFRACTORY BRICKS :  This is one of the most widely used types of fire bricks. They are made from a mixture of quartz and pure calcium oxide. Quartz is transformed into calcium silicate during the production phase. Silica refractory bricks are mainly used in the construction of metallurgical furnaces. Their resistance to acid-based abrasion is high.

MAGNESITE REFRACTORY BRICKS : They are manufactured from periclase and belong to the basic refractory category. Periclase acts like a mortar and bonds the iron oxide, quartz, and silicate together. It has a high tolerance against basic corrosion. However, their resistance to high temperature is low. They are used in basic furnaces of all types.

CHROMITE-MAGNESIA REFRACTORY BRICKS   : As the name suggests, they are made from a mixture of magnesite and chromite content. (Mixing ratio is usually 70/30.) They are manufactured with the dry-pressing method. Furnace ceilings and gas outlet pipes are the most common areas of usage.

DOLOMITE REFRACTORY BRICKS : They are made of dolomite, which is an extremely common material. Dolomite bricks are used in chambers of basic and electric arc furnaces, and over the inner walls. 

Refractory installation is a task that needs to be treated carefully at every stage. The preceding stage is of vital importance at least as the refractory installation phase. The preparations required before the installation stage can be reviewed under two category:

Before moving on to the construction site

Like all projects, refractory installation begins with the collection of necessary documents. Therefore, it is important to collect all of the documents before going to the construction site. Examples of these documents are order confirmations, schedules, maps, and material supply schematics. Installation instructions and safety data sheets are also a part of required documents. The status of preliminary work must be checked beforehand too; for example, whether the removal of the old refractories is finished or not. Preparing a work schedule will also be extremely useful. All construction / installation works, furnace components, and structures should be divided into easy-to-follow steps in this working schedule.

Preparations on the construction site

The first thing to look for is the storage conditions of the related equipment and materials in the construction site. In other words, the equipment placement and availability must be confirmed beforehand. Accessibility of the construction site for materials, electricity, drinking water, compressed air and waste disposition should also be considered in this context. Construction sites must contain appropriate construction equipment, building piers and the staff should be equipped with the necessary tools. Moving work platforms, pumps and welding equipment used for the implementation of refractory mortars are some examples of appropriate construction equipment. All refractory materials must be placed in a certain order for easy access. In this context, the presence of a storage compartment is essential to protect them from the weather. Safety instructions should be explained to staff before starting the installation process. All of these issues must be regularly checked during the project. 

Refractory materials, like all other industrial materials, have a limited lifetime. After the end of their lifespan, they won’t be able to fulfill their purpose. In other words, they start to degrade at elevated temperatures or corrosive chemical components. Refractory materials will fill their lifespan even if they are not subject to an accident. Once this happens, removal of the refractory material and recycling becomes mandatory. Eradication of wasted materials is possible, although recycling process will prevent harm to the environment and help reduce the cost of reconstruction.

Refractory lifespan

The lifespan of refractory materials depends on the capabilities of the refractory material used. Likewise, exposure to erosion / corrosion levels will also affect the situation. The care shown during installation and the frequency of maintenance will directly reduce or improve the lifetime too. To give an example, a glass melting furnace coated with AZS (aluminum – zirconia – silica) has a lifespan of 14 – 18 years, if all maintenance jobs are done in time. The same furnace with a different coating material other than AZS will be subject to a lifespan of 6 – 8 years. In other words, the lifespan of refractory materials depends on a number of elements that needs to be evaluated together.

How long will refractory materials last?

Assembly and preparation for the installation are the most important matters for industries which use refractory materials. Working only with experts and companies with a background in the sector should be preferred. Because even the slightest mistake during production and installation will affect the lifespan of refractory materials in a negative way. Likewise, periodic maintenance and as well as hot & cold repair needs should not be neglected. Regular maintenance and repair will greatly improve the lifetime of refractory materials. Upon addressing these issues, it is possible to easily obtain a lifespan reaching tens of years.

These terms are related to the refractory materials industry, and especially industrial furnaces. An industrial furnace built with refractory materials is subject to a variety of processes during the installation and maintenance. To specify these processes in detail:

HOT REPAIR : Hot repair is the term used for maintenance and repair operations performed without stopping the operation of an industrial furnace. In other words, the process is completed while the furnace is still running at high temperature. This ensures that businesses do not lose time and money.

HEAT – UP : After the construction of an industrial furnace is completed, the first heating of the furnace must be done in a controlled manner. Heat - up is a term that refers to this process. The first heating of the furnace is an extremely delicate process. Even one wrong move during this operation will directly affect the lifetime of the refractory materials and the furnace. The heat - up process differs depending on the refractory material used in the furnace. For example, alkali-containing refractory materials release very little water vapor during the first heating. However, furnaces built with conventional refractory materials will release a dense water vapor and require appropriate measures. The heat - up process must be completed without reducing the thermal stability of refractory materials. Convective heat transfer is the most commonly used method for heat-up processes.

DRY OUT : Dry out literally means "drying" and is a very important process for the refractory materials to be ready for use. Monolithic refractories contain an amount of liquid and moisture inside. As explained above, more moisture and liquid also occurs during the heat - up process. Dry – out is the name of the process which removes all of this unwanted liquid and moisture and completely dries up the furnace. Otherwise, moisture remaining in the materials will reduce the long-term stability and reduce the lifespan of industrial furnaces. How the dry - out method is carried out depends on the nature of the refractory material used.