Refractory materials for glass melting furnaces
In addition to the high-temperature performance we mentioned earlier, the physical properties of refractory materials for glass melting furnaces are also very important when purchasing. The physical properties of the product are closely related to the actual service life. The specific items that need to be referred to are:
Organization structure
Refractory materials are heterogeneous bodies composed of two parts: solid phase (including crystal and glass phase) and pores. The macroscopic organizational structure characteristics of the product are the main factors affecting its high-temperature performance.
① Porosity
In refractory materials, there are often many pores of different sizes and shapes. Those that are connected to the atmosphere are called open pores (also called apparent pores), those that penetrate each other are called connected pores, and those that are not connected to the atmosphere are called closed pores. Porosity is usually used to reflect the density of refractory materials, that is, the percentage of pore volume in bricks to the total volume.
Porosity is a basic technical indicator of refractory materials, which almost affects all the properties of refractory products. The smaller the porosity, the better the erosion resistance of the refractory material and the higher the structural strength. The higher the porosity, the lower the thermal conductivity of the material.
② Bulk density
The bulk density is the mass of a refractory material per unit volume (total volume including pores). It intuitively reflects the density of refractory products and is an important indicator for measuring the quality level of refractory materials and dense refractory products. Generally speaking, the higher the bulk density, the smaller the porosity, and the better the series of properties such as strength and high temperature load softening temperature.
③ True density
True density refers to the ratio of the mass of a porous material to its true volume (excluding pores). True volume refers to the volume of solid material in a porous body. Its value has nothing to do with density and porosity, but is related to the chemical mineral composition of the refractory material.
Thermal properties
① Thermal expansion
When a refractory material is heated, the property that its volume expands with the increase in temperature is called thermal expansion. It is usually expressed by linear expansion coefficient or volume expansion coefficient.
When using refractory materials, their thermal expansion must be taken very seriously. Expansion joints should be reserved in the melting furnace structure according to the characteristics of the thermal expansion of the refractory materials. When igniting the kiln, a reasonable heating curve should be formulated according to the thermal expansion of the refractory materials and necessary measures such as adjusting the tie rods should be adopted.
② Thermal conductivity
Thermal conductivity indicates the thermal conductivity of the refractory material, which is expressed by thermal conductivity. The so-called thermal conductivity refers to the heat flow rate through the unit area of the material under the unit temperature gradient. It mainly depends on the chemical composition and organizational structure of the material.
③ Heat capacity
Thermal capacity, also known as specific heat capacity, refers to the heat required to heat 1kg of refractory material to raise its temperature by 1°C under normal pressure. It is of great significance in designing and controlling the heating and heat storage capacity of the melting furnace.
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