What are the requirements for lime in the metallurgical industry
Lime, as an important flux and slagging material, has a critical impact on the quality of metallurgical production processes and products. The specific requirements are as follows:
In terms of chemical composition
Require a calcium oxide (CaO) content of not less than 90%, a magnesium oxide (MgO) content of not more than 1.5%, an effective alkalinity of not less than 85%, an active calcium content of not less than 75%, a sulfur content of not more than 0.1%, and an iron oxide content of not more than 0.5%. For example, in steelmaking, CaO and SiO ₂ are the basis for preparing slag alkalinity. The lower the SiO ₂ and the higher the CaO, the better. Generally, SiO ₂ should be less than 1.2%, otherwise it is easy to form a thin film on the surface of lime, which seriously hinders slagging.
In terms of physical performance
The limestone content shall not exceed 5%, and the ash content shall not exceed 3%. In terms of particle size distribution, the material passing through a 60 mesh sieve should not be less than 95%, and the material passing through a 200 mesh sieve should not be more than 10%. The lower limit of lime block size for oxygen converter steelmaking is generally specified as 6-8mm, and the upper limit is recommended to be 30-40mm.
Other requirements
Lime is prone to water absorption and pulverization, becoming ineffective Ca (OH) ₂. Therefore, new lime should be used and the storage time should be limited. Before use, it should be baked at around 800 ℃ for 2-3 hours to remove absorbed moisture. Activity is an important parameter for measuring the quality of lime. According to Chinese standards, active lime is defined as active lime with an activity level greater than 310ml. Active lime has strong reaction ability, can accelerate slag formation rate, and improve dephosphorization and desulfurization efficiency.
