Refractory work lining erosion is usually classified as chemical, thermal and mechanical erosion, which can occur singly or in combination, and the damage to the refractory can be continuous (dissolution and erosion) or discontinuous (cracking and spalling), with spalling leading to discontinuous local separation of the refractory bricks and severe slag infiltration culminating in densification of the bricks close to the hot face. . The difference in thermal expansion properties between the densified and non-penetrated areas creates large internal stresses, which eventually lead to the formation of cracks and cracking. In general, strong thermal shock leads to thermal spalling.
This paper focuses on the physical erosion of refractories for copper smelting furnaces, i.e. 'thermal erosion' and 'mechanical erosion'. This is to understand the working conditions of refractory materials in copper smelting furnaces and to better and more effectively extend the service life of the furnace lining.
1. Thermal erosion
2.1.1 Temperature
Although the serviceable temperature of refractories used in copper smelting furnaces (1600-1700°C) is much higher than the actual service temperature of copper smelting furnaces, the temperature of copper smelting furnaces plays an important role in the continuity of refractory erosion. Through interfacial reactions with substances in the melt pool, the high-temperature strength of the refractory bricks is significantly reduced, and the elevated temperature clearly leads to a reduction in the viscosity of the high-heat molten slag, increased diffusivity and faster erosion.
1.2 Thermal shock
Temperature fluctuations caused by interruptions and irregularities in the operation of the furnace can cause stresses within the refractory bricks, and such stresses, once they exceed their limit values, can lead to cracks within the refractory bricks. Interfacial reactions between the furnace charge and the refractory bricks can densify the structure and adversely affect the refractory bricks' ability to absorb stress. The thermal shock stability of refractory materials increases with increasing material toughness and thermal conductivity, and increases with decreasing coefficient of thermal expansion and modulus of elasticity. A large ratio of modulus of rupture to modulus of elasticity will reduce the formation of cracks and improve the elasticity of the material.
2. Mechanical erosion
2.1 Abrasion
Abrasion is firstly caused by the movement of materials in the smelting furnace (including liquid metal, slag, furnace charge and dust formed after gas volatilisation), and secondly by the spraying of materials into the furnace during certain special processes, all of which are factors that lead to continuous erosion of the furnace lining refractory.
2.2 Collision stress
The stress effects of knocking, colliding and grinding caused by blowing material into the smelting furnace cause cracks to form in the refractory and wear of the refractory.
2.3 Mechanical fatigue
The causes and results of mechanical fatigue are similar to those of thermal fatigue, with the difference that mechanical fatigue affects a deeper area in the refractory bricks than thermal fatigue, and that mechanical fatigue tends to be more important for rotary kilns with cyclically changing loads.