A variety of lime products are used in the production of steel in the basic oxygen process (BOP). This process includes basic oxygen furnace (BOF), QBOP and KOBM furnaces. Silicon oxides are produced during the oxidation of the liquid pig iron from the blast furnace that are detrimental to refractory performance during this steelmaking process. Lime is critical in producing a slag through the “mass balance” approach to assure the correct chemistry for the ideal slag basicity.
In this steelmaking process, it is common to see high calcium pebble lime and dolomitic pebble lime being charged overhead into these furnaces. In addition, pulverized high calcium flow aided lime or a blended high calcium/dolomitic pulverized flow aided lime is injected through tuyeres in the bottom of the QBOP and KOBM with oxygen which provides fast dissolution of the fluxes and improved de-phosphorization.
- High Calcium pebble lime is key to neutralizing “acid oxides” from the oxidation of silicon in the “hot metal” coming from the blast furnace to the BOF. Additionally, CaO is important for removal of phosphorous in the steelmaking BOF process. It is the CaO/SiO2 relationship that influences the MgO demand of the slag.
- Dolomitic pebble lime additions provide the MgO saturation for basicity conditions to provide the refractory protection in the BOF. The slag contains dissolved calcium oxide and silica that cause MgO to dissolve from refractory brick into the slag. MgO will dissolve into the slag based on relationships of FeO content, basicity and temperature.
Pulverized lime – High Calcium or Blended is a specialized product that provides removal of impurities in the liquid pig iron during oxidation to form slag in the BOP process. This product can be high calcium by itself or a blended product of high calcium and dolomitic lime.