Refractory is a type of material which is designed for use in high heat environments such as kilns and furnaces. The refractory materials can be categorized into many types. When choosing refractory materials, it is not only the problem of the best but also the right.
The primarily important requirement of refractory brick is that it can withstand very high temperatures without failing. It also needs to have low thermal conductivity, which is designed to make operating environments safer and more efficient. Furthermore, refractory brick can withstand impact from objects inside a high heat environment, and it can contain minor explosions which may occur during the heating process.
The most important factors to consider are the area of application and the operating environment. Selecting materials should always be based on properties and specifications suitable for the specific application and operating conditions.
First identify the area of application. Refractories can be used for a wide variety of different applications. Using refractory materials which are not right for the specific application can be dangerous. The refractory materials may fail, cracking, exploding, or developing other problems during use which could pose a threat to safety in addition to fouling a project.
If the refractory material is destined for heating or cooking, you may choose a normal refractory such as the fire brick. This not only heats up quickly, but also withstands many duty cycles of heating and cooling without breaking.
Some applications may require special refractory materials. Zircon is used when the material must withstand extremely high temperatures. Silicon carbide and carbon are two other refractory materials used in some very severe temperature conditions, but they cannot be used in contact with oxygen, as they will oxidize and burn.
Then consider the operating environment, the thermal environment and the chemical environment. Each application is going to require a different type of refractory based on the temperatures, likelihood of chemical corrosion and other issues that need to be taken into consideration. There are three general, acidic refractories, neutral refractories, and basic refractories. Be sure to select the corresponding chemical properties of refractories, otherwise chemical changes occur at high temperatures. Acid refractories are used in areas where slag and atmosphere are acidic. Neutral refractories are used in areas where slags and atmosphere are either acidic or basic. Basic refractories are used on areas where slags and atmosphere are basic.
Choosing the right refractory materials is not a simple thing. Besides of the application and operating environment, there are still many other factors to consider, such as the service life and costs.