Mathematical Modeling of the Energy Consumption and Carbon Emission for the Oxygen Blast Furnace with Top Gas Recycling

The ironmaking process is the most significant source of CO₂ emission in the iron and steel industry, which generates large quantities of greenhouse gases. Recently, oxygen blast and top gas recycling have been applied to the blast furnace to improve the energy efficiency and reduce the pollution from the ironmaking process. However, as a new ironmaking technology, the oxygen blast furnace with top gas recycling (TGR‐OBF) is still under development. This paper focuses on the investigation of the energy consumption and carbon emission for the TGR‐OBF process by modeling the stack, the bosh, the combustion zone, and the gas recycling system. Effects of the key parameters in the TGR‐OBF process on the carbon consumption of reactions and the energy consumption of the system are investigated by orthogonal experiments. Our results indicate that the TGR‐OBF process has the advantages of reducing energy consumption and CO₂ emission. The low temperature and high reducing environment in the new furnace is favorable to lower the coke gasification and increase the reaction rate of iron oxide. The recycling of the top gas can significantly reduce CO₂ emission, and the main advantage comes when the stripped CO₂ is stored.     

Bainite Growth Behavior at Early Stage of Transformation in a High Carbon Silicon-Containing Steel

 The growth behavior at the early stage of bainitic transformation was investigated using optical microscopy, X-ray diffraction analysis and transmission electronic microscopy. The bainite was obtained by isothermal transformation at 200 ℃ only for a short time in a high carbon silicon-containing steel after austenitization at 200 ℃ only for 20 min. Transmission electronic microscopy shows that the bainite appears in the form of plates with a width of about 30 nm, and that the interface of the bainite leading tip is wedge shaped. X-ray diffraction analysis reveals that the bainite plates consist of single ferrite phase, with absence of carbides. The results confirm the occurrence of the moiré which suggests the existence of austenite grain boundaries at the bainite leading tip. Both the lateral growth and longitudinal growth of bainite have weak ability to traverse the lattice-distortion strain fields and austenite grain boundary. The austenite grain boundary impedes the longitudinal growth of the bainite plate, i. e. , the growth of bainite plate stops at the austenite grain boundary. The longitudinal growth of bainite associated with the features of shear mechanism can not completely be in accordance with that of martensitic transformation.