Refractory balls are spherical refractory products that can store heat. They are high-temperature heat storage materials used in hot blast furnaces and heating converter regenerators.
There are three main types of refractory balls: made of siliceous, high-alumina, and magnesia refractory materials. According to the chemical composition, they are divided into five types: high-alumina balls, zirconium corundum balls, chromium corundum balls, aluminum-zirconium-chromium composite balls, and low creep balls.
What is the difference between refractory balls and heat storage balls?
1 Recycling value:
The biggest difference between heat storage balls and refractory balls is that heat storage balls cannot be recycled, while refractory balls can be recycled and reused.
2 Different raw materials:
The heat storage ball is made of alumina as the main raw material. After reasonable calcination and molding, it is calcined at high temperature. The surface of the product is relatively delicate and the color is slightly white.
Refractory balls are made of industrial alumina and kaolin as important raw materials. The color is a little yellow and the surface is rough.
3 Different properties:
Refractory balls have the advantages of high strength, wear resistance, high thermal conductivity, large heat capacity, high heat storage efficiency, good thermal stability, and not easy to break when the temperature changes suddenly.
The strength of the refractory ball is also relatively high, and it is relatively wear-resistant. Its thermal conductivity and heat capacity are relatively large, and its heat storage efficiency is also relatively high.
4 Different uses:
The heat storage ball is suitable for the selection of the heat storage ball combustion system of gas and non-gas industrial furnaces, especially for the heat storage furnace of the steel industry, the heat storage ladle roaster, the air separation equipment heat storage in the air separation industry, and non-ferrous metals. The heat storage melting furnace in the metal industry can also be used as a heat storage carrier, such as the heat storage trolley furnace, the heat storage electric boiler, and the heat storage incinerator of a large forging plant.
The heat storage ball is divided into a solid ball and a concave and convex hole. The solid ball has excellent mechanical strength, strong acid and alkali corrosion resistance and excellent thermal shock resistance. It is mainly used in high temperature, high pressure and corrosive working environments in general petroleum, fertilizer, petrochemical and other chemical industries. It is particularly suitable for heat storage fillers in steel plant air separation equipment and blast furnace gas heating furnaces. Through the dual preheating of coal gas and air, the combustion temperature can quickly reach the requirements of steel rolling heating billets.
The environmental protection effect of heat storage balls is very good, which is in line with my country’s environmental protection policy. I believe that the development of heat storage balls will become more and more extensive in the future.
Refractory balls have the characteristics of high strength, high hardness, strong wear resistance, strong specificity, small size, high temperature resistance, corrosion resistance, and no pollution. They are widely used in various ceramics, enamel, glass, chemical and other industries. Our factory performs fine processing and deep processing on thick and hard materials.
Refractory balls are divided into ordinary refractory balls and high-aluminum refractory balls. Ordinary refractory balls are suitable for converters and converters in sulfuric acid and fertilizer industries, and high-aluminum refractory balls are suitable for hot blast furnaces and heating converters in urea, steel and other industries.
Introduction to refractory ball indicators
1.1 Thermal expansion
GB/T7320 standard has two definitions: linear expansion rate (relative change rate of refractory ball diameter from room temperature to test temperature, unit is %), average linear expansion rate (relative change rate of sample length for every 1°C increase between room temperature and test temperature, unit is 10-6/℃)
The measurement principle of GB/T7320 standard is: heat the sample to the specified test temperature at a specified heating rate, measure the change of sample length with the increase of temperature, and calculate the range of linear expansion rate of the sample with the increase of temperature and the average linear expansion coefficient of the specified temperature, and draw the expansion curve.
1.2 Thermal conductivity
The thermal conductivity is defined as: the heat passing through the unit area of the refractory ball in the direction of heat flow under unit temperature gradient per unit time.
The principle of measuring thermal conductivity is: according to the basic principle of Fourier one-dimensional plate steady-state heat conduction process, measure the heat flow in the one-dimensional temperature field per unit time under steady state, through the hot surface of the sample to the cold surface longitudinally, and then measure the water flow through the central calorimeter. Absorb heat. The heat is proportional to the thermal conductivity of the sample, the temperature difference between the hot and cold surfaces, and the area of the central calorimeter heat absorption surface, and inversely proportional to the thickness of the sample.
The physical meaning of thermal conductivity refers to the amount of heat that passes through a unit vertical area per unit time under a unit temperature gradient. Thermal conductivity is a physical indicator that characterizes the thermal conductivity of refractory balls, and its value is equal to the heat flux divided by the negative temperature gradient.
1.3 Heat capacity
Any substance will heat up when heated, but different substances of the same mass require different amounts of heat to heat up by 1°C. It is usually expressed by the amount of heat (KJ) required to heat 1kg of material at normal pressure to raise its temperature by 1°C, which is called heat capacity (also known as specific heat capacity).
1.4 Conductivity
Refractory balls (except carbon and graphite products) are poor conductors of electricity at room temperature. As the temperature increases, the resistance decreases and the conductivity increases. This increase is particularly significant when the temperature is above 1000°C. When heated to a molten state, it will show great conductivity.
Mechanical properties
The mechanical properties of refractory balls refer to the strength, elasticity and plasticity of refractory balls at different temperatures. The mechanical properties of refractory balls are usually judged by test indicators such as compression resistance, bending resistance, wear resistance, and high-temperature soft creep.
Performance analysis
Refractory balls are of four types: high-aluminum, silicon, magnesium-aluminum, and porcelain balls.
At present, there are many high-aluminum refractory balls on the market, most of which are used in ball-type hot blast furnaces below 450m3. Refractory balls for ball-type hot blast furnaces are divided into four specifications according to diameter size: φ40mm, φ50mm, φ60mm, and φ80mm. They can also be produced according to user requirements. The refractory balls in the regenerator of the hot blast furnace will be affected by periodic alternation of hot and cold at high temperatures, and will be corroded or bonded by alkaline gas dust. High-aluminum refractory balls are used in the high-temperature area above the ball bed. The refractoriness and load softening temperature can meet the requirements, but the thermal stability and slag resistance are insufficient. Surface cracks and slag will appear, resulting in poor bed permeability and shortening the cleaning cycle.
The silicon content of silicon refractory balls is 92%, and they have strong resistance to acid slag corrosion, but poor low-temperature thermal stability. Silica refractory balls are used in the high temperature zone above the pebble bed. Under the conditions of high temperature and large gradient temperature change, the ball surface cracks are serious, the resistance to alkaline gas dust erosion is poor, the slagging is serious, and the balls are difficult to clean.
The core of the ball heat furnace is the ball bed. The pebble layer is formed by the natural accumulation of equal-diameter refractory balls, which can be divided into upper and lower levels according to the different ball diameters and materials. What kind of balls are used in the high temperature zone? Look at the performance of magnesium refractory balls.
Magnesium oxide refractory balls have strong resistance to alkali slag corrosion. The thermal stability and volume stability are poor, but the thermal conductivity is strong. In addition to the advantages of magnesium oxide refractory products, it also has high thermal stability. Compared with magnesium aluminum refractory balls, the thermal conductivity, heat capacity and thermal conductivity of magnesium aluminum refractory balls are greatly improved, and their thermophysical properties are superior.
Compared with high aluminum refractory balls and silicon refractory balls, magnesium aluminum refractory balls have higher material density, increased unit bed mass and bed mass coefficient. Magnesium aluminum refractory balls have stable high temperature performance. It can be used safely for a long time under the temperature condition of 1350～1450℃ in the upper high temperature zone of the spherical hot blast furnace.