What are the ways to reduce the spalling of refractories?

The damage of refractories in high temperature furnaces or containers is mainly the comprehensive result of physical and chemical action of environment and erosion medium on refractories. Because of the use of different conditions, its damage causes are different; Sometimes physical action is dominant, sometimes chemical action is dominant. For example, the refractories used in hot blast furnaces and regenerator chambers of some kilns will be damaged or collapsed due to deformation under high temperature load. Generally, it is mainly caused by melting erosion, scouring and thermal spalling and structural spalling caused by temperature fluctuations.

The melt has good wettability to refractories, indicating that it has great affinity with refractories, indicating that the melt is easy to act or react with refractories, so that the surface of refractories is subjected to melting erosion and chemical erosion. Usually, the porosity of refractories is large. If the melt has good wettability to refractories, the melt will penetrate into the refractories along the pores, cracks and other capillary channels. When the dihedral Angle between the melt and the grain is zero, the melt will permeate along the grain boundary and disperse, so that the refractory particles are dismembered.

The melt inside infiltrates the refractory material and the refractory element interaction, thus forms with the original refractory material structure and property different metamorphic layer when the temperature in the furnace produces violent fluctuation, this metamorphic layer will occur cracking, peeling, this kind of cracking, peeling is called structure peeling. Structure spalling is not like dissolution, erosion that only makes the surface of refractory brick gradually erosion; But a few millimeters, tens of millimeters thick large areas suddenly peeling off. Therefore, it is very harmful to the life of furnace lining.

Obviously, the deeper the melt penetration, the thicker the metamorphic layer, the more serious the damage of structure spalling, intermittent production furnace, due to the furnace temperature fluctuation, and frequent, so the structure spalling is often the main cause of furnace lining damage.

Reducing the radius of refractory pores or pores, increasing the contact Angle, increasing melt viscosity, and reducing melt surface tension can reduce the depth of melt infiltration into refractory, so as to reduce the structure spalling.

After the melt and refractory material, such as the formation of a large viscosity of melt, or the formation of high melting point compounds precipitated crystal or formed a protective layer, so that the infiltration channel blocked, can also prevent the infiltration of slag, reduce the structure of spalling.

From the above analysis, it can be concluded that the ways to reduce the spalling of refractory materials are as follows:

(1) adding refractory elements with bad melt wetting in refractory materials, such as carbon, graphite, carbide or nitrous oxide can be added in slag infiltration resistance; The composite material containing carbon or non-oxide is made.

(2) Add components that can form high melting point or viscous substances with melt to refractory materials to hinder melt infiltration.

(3) make refractory pores or pores micro fine, made of micro pores or ultra-micro pores refractory, so that the melt infiltration is very shallow. For example, microporous or ultramicro carbon bricks are now available.

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