Reaction Properties of Basic Oxygen Furnace Slag and Methane in a Fluidized-Bed Chemical Looping System

In the conventional steelmaking process, slag is the second-largest byproduct. Although most slags have ways to be reused, the demand for small BOF (basic oxygen furnace) slag is still limited. This study aimed to develop a fluidized-bed chemical looping system using BOF slag as an oxygen carrier and methane as a fuel to produce heat for the steelmaking process. The results of the BOF slag reaction test on a batch fluidization and reaction test facility indicated that the methane conversion rate increased with an increase in the methane concentrations and the reaction temperature. As methane concentration increased from 5 to 15 v/v % at the reaction temperature of 950 °C and the fluidized velocity of 5.1 times the minimum fluidized velocity of BOF slag, the methane conversion rate increased from 65.8 to 76.6%. By setting 10 v/v % as the referenced methane concentration, the methane conversion rate corresponded to 71.6%, and as the reaction temperature increased to 980 °C, the methane conversion rate of 85.7% was achieved. The fluidized gas velocity influenced the fluidized state of the oxygen carrier and the gas residence time in the reactor. As the gas velocity was 1.9 times the minimum fluidization velocity of BOF, the methane and oxygen carrier conversion rates reached 83.3 and 13.0% at the referenced methane concentration and reaction temperature of 950 °C. The experimental results could offer the required design and operation parameters for the methane fluidized bed chemical looping system using BOF slag as the oxygen carrier.